android: Share → ThoughtSync, and a "New note" entry in the selection toolbar

Capture without opening the app first — the input half of #1899. Two ways in:
the share sheet from anywhere, and the text-selection toolbar in any app's
text field.

## The note is created, not pre-filled

The obvious build is "open the editor on a draft holding the shared text".
That silently loses it. `NoteEditorScreen`'s flush is guarded by
`bodyText != note.body`, so a draft handed the text already has nothing to
save — share a link, press back without typing, and it is gone. Which is
exactly the shape of a share: the common case is walking away.

So `captureShared` makes the row first and opens the editor on the real
note. A share has already said "keep this"; creating it is what honours
that, and back then leaves a saved note rather than a decision.

## launchMode="singleTop"

The reminder notification adds FLAG_ACTIVITY_SINGLE_TOP to its own intent,
which is why `onNewIntent` already worked there. A share intent is built by
the OTHER app and nothing here can add a flag to it, so the activity has to
declare it. Without that, every share while the app was running would stack a
second MainActivity — a second view model, a second board, and a back press
landing on a stale copy of the same app.

## Subject and text, both

A browser sends EXTRA_SUBJECT as the page title and EXTRA_TEXT as the URL.
Keeping both makes the note read as its title, because the core names a note
by its first line — the difference between a board you can scan and a column
of identical links. `distinct` because plenty of senders put the same string
in both.

The extras are removed on read, like the reminder's note id and for the same
reason: the activity keeps its launch intent, so without consuming them a
rotation would replay the share and mint the note again.

## Not included: images

`image/*` is deliberately absent from the filter. Nothing in this app can
create an attachment — the core has `delete_attachment` and no counterpart,
and the FFI exposes neither. Declaring the mime type would put ThoughtSync in
front of people in the share sheet for a job it cannot do, and fail after
they had already chosen it. Adding it needs an attachment-creation path
through the core, the FFI and sync, which is its own piece of work.

The desktop half of #1899 — a global hotkey — is not in this commit.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K3MMqUtzX1TJgA1oypvm1c

android/app/src/main/AndroidManifest.xml

@@ -99,15 +99,53 @@
         android:supportsRtl="true"
         android:theme="@style/Theme.ThoughtSync"
         android:usesCleartextTraffic="true">
+        <!--
+          launchMode="singleTop" exists for the SHARE filters below.
+
+          The reminder notification adds FLAG_ACTIVITY_SINGLE_TOP to its own
+          intent, so onNewIntent already worked for that one. A share intent is
+          built by the OTHER app — Chrome, a reader, the text-selection toolbar —
+          and nothing here can add a flag to it. Without singleTop declared on the
+          activity itself, every share while the app is running would stack a
+          second MainActivity on top of the first: a second view model, a second
+          board, and a back press that lands on a stale copy of the same app.
+        -->
         <activity
             android:name=".MainActivity"
             android:exported="true"
+            android:launchMode="singleTop"
             android:windowSoftInputMode="adjustResize"
             android:theme="@style/Theme.ThoughtSync">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
+
+            <!--
+              Capture without opening the app first: Share → ThoughtSync from
+              anywhere, and the selection toolbar in any text field.
+
+              text/plain ONLY, and image/* deliberately absent. Nothing in this
+              app can create an attachment — the core has `delete_attachment` and
+              no counterpart, and the FFI exposes neither. Claiming images in the
+              share sheet would put this app in front of people for a job it
+              cannot do and fail after they had chosen it.
+            -->
+            <intent-filter>
+                <action android:name="android.intent.action.SEND" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <data android:mimeType="text/plain" />
+            </intent-filter>
+
+            <!--
+              The label is what appears in the text-selection menu beside Copy and
+              Share, where "ThoughtSync" would say who rather than what.
+            -->
+            <intent-filter android:label="@string/capture_process_text">
+                <action android:name="android.intent.action.PROCESS_TEXT" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <data android:mimeType="text/plain" />
+            </intent-filter>
         </activity>
 
         <!--

android/app/src/main/java/com/fabledsword/thoughtsync/MainActivity.kt

@@ -53,12 +53,24 @@ class MainActivity : ComponentActivity() {
      */
     private val requestedNote = mutableStateOf<String?>(null)
 
+    /**
+     * Text shared into the app from elsewhere, waiting to become a note.
+     *
+     * Same shape and same reason as [requestedNote]: a share that arrives while
+     * the app is already running lands in [onNewIntent], long after the
+     * composition was built, so a piece of state it is already reading is the only
+     * way in. The activity is `singleTop` in the manifest precisely so that this
+     * path exists for an intent another app built.
+     */
+    private val sharedText = mutableStateOf<String?>(null)
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
 
         val app = application as ThoughtSyncApplication
         requestedNote.value = takeRequestedNote(intent)
+        sharedText.value = takeSharedText(intent)
 
         setContent {
             ThoughtSyncTheme {
@@ -69,7 +81,7 @@ class MainActivity : ComponentActivity() {
                     // than render an empty board that looks like data loss.
                     StoreUnavailableScreen(reason = app.openFailure)
                 } else {
-                    App(core, requestedNote)
+                    App(core, requestedNote, sharedText)
                 }
             }
         }
@@ -79,6 +91,7 @@ class MainActivity : ComponentActivity() {
         super.onNewIntent(intent)
         setIntent(intent)
         requestedNote.value = takeRequestedNote(intent)
+        sharedText.value = takeSharedText(intent)
     }
 
     /**
@@ -94,6 +107,54 @@ class MainActivity : ComponentActivity() {
         intent.removeExtra(Reminders.EXTRA_NOTE_ID)
         return id
     }
+
+    /**
+     * Read the text a share or a text selection brought in, and CONSUME it.
+     *
+     * Consumed for the same reason [takeRequestedNote] is: the activity keeps the
+     * intent it was launched with, so without removing the extras a rotation would
+     * replay the share and mint the same note again, with nothing on screen to
+     * explain where the duplicates were coming from.
+     */
+    private fun takeSharedText(intent: Intent?): String? {
+        val shared =
+            when (intent?.action) {
+                Intent.ACTION_SEND -> intent.takeSendText()
+                Intent.ACTION_PROCESS_TEXT -> intent.takeProcessText()
+                else -> null
+            }
+        return shared?.takeIf { it.isNotBlank() }
+    }
+}
+
+/**
+ * The shared text, with a subject line above it when the sender gave one.
+ *
+ * Sharing a page from a browser sends EXTRA_SUBJECT as the page title and
+ * EXTRA_TEXT as the URL. Keeping both makes the note read as its title, because
+ * the core names a note by its first line — so this is not decoration, it is what
+ * turns a board of identical-looking links into a board you can scan.
+ *
+ * `distinct` because plenty of apps put the same string in both, and a note that
+ * says the URL twice is worse than one that says it once.
+ */
+private fun Intent.takeSendText(): String? {
+    val body = getStringExtra(Intent.EXTRA_TEXT)
+    val subject = getStringExtra(Intent.EXTRA_SUBJECT)
+    removeExtra(Intent.EXTRA_TEXT)
+    removeExtra(Intent.EXTRA_SUBJECT)
+    return listOfNotNull(subject, body)
+        .map { it.trim() }
+        .filter { it.isNotEmpty() }
+        .distinct()
+        .joinToString("\n")
+}
+
+/** The selection from another app's text field, via the selection toolbar. */
+private fun Intent.takeProcessText(): String? {
+    val text = getCharSequenceExtra(Intent.EXTRA_PROCESS_TEXT)?.toString()
+    removeExtra(Intent.EXTRA_PROCESS_TEXT)
+    return text
 }
 
 /** Which screen is up. Exactly one at a time. */
@@ -115,6 +176,7 @@ private enum class Screen { BOARD, EDITOR, SYNC, TAGS }
 private fun App(
     core: ThoughtSync,
     requestedNote: MutableState<String?>,
+    sharedText: MutableState<String?>,
 ) {
     val context = LocalContext.current
     val board: BoardViewModel =
@@ -137,6 +199,15 @@ private fun App(
         }
     }
 
+    // Cleared the same way and for the same reason: without it every later
+    // recomposition would capture the shared text again as a new note.
+    LaunchedEffect(sharedText.value) {
+        sharedText.value?.let {
+            board.captureShared(it)
+            sharedText.value = null
+        }
+    }
+
     ReminderAlarms(core)
     // A pull can rewrite every note the board is holding, so a sync that changed
     // anything tells it to reload. Wired here, at the one place that owns both.

android/app/src/main/java/com/fabledsword/thoughtsync/ui/BoardViewModel.kt

@@ -256,6 +256,32 @@ class BoardViewModel(
         state = state.copy(editing = blankDraft(), editingSession = state.editingSession + 1)
     }
 
+    /**
+     * Capture text shared into the app from somewhere else, and open it.
+     *
+     * The note is CREATED here rather than opened as a pre-filled draft, and that
+     * is the whole design of this path. The editor only flushes when its text
+     * differs from the note it was handed (`NoteEditorScreen`'s `flush`), so a
+     * draft arriving already full of the shared text is a draft with nothing to
+     * save — share a link, press back without typing, and it would be gone. A
+     * share has already said "keep this"; making the row first is what honours it.
+     *
+     * Opening the editor afterwards is then free of that risk: the note exists,
+     * back leaves it alone, and adding a line of context is optional rather than
+     * load-bearing.
+     */
+    fun captureShared(text: String) {
+        val content = text.trim()
+        if (content.isEmpty()) return
+        // A share is a new sitting even if the editor was already open on
+        // something, so the field must be re-keyed onto what arrives. `createFrom
+        // Draft` deliberately does not bump this — it is written for the autosave
+        // case, where re-keying mid-typing would be the bug.
+        draftDismissed = false
+        state = state.copy(editingSession = state.editingSession + 1)
+        createFromDraft(content)
+    }
+
     /**
      * Set when a draft's editor closes, so a create still in flight does not reopen
      * it. The editor flushes its text and then closes, and the flush is a coroutine —

android/app/src/main/res/values/strings.xml

@@ -66,6 +66,11 @@
     <string name="editor_delete_forever_body">It will be removed from this device and from every device you sync with. This cannot be undone.</string>
     <string name="editor_delete_forever_confirm">Delete</string>
 
+    <!-- Quick capture from outside the app: the share sheet and the text-selection
+         toolbar. "New note" says what happens; the activity's own label would say
+         who it happens in. -->
+    <string name="capture_process_text">New note</string>
+
     <!-- Tag management. The whole vocabulary is "tag" (see Scribe #2966); the
          schema still says Label, and no string here needs to know that. -->
     <string name="tags_manage">Manage tags</string>