core: shared notes on the desktop and phone, and Share from the desktop

The core pulls with shares from a server offering them (protocol 6): a note
says how it is held (owner, edit, view) and who shared it, and a revoked note
leaves the device. The first such pull starts the feed over once, so notes
shared before this build arrive. The store refuses what a share doesn't allow
(view: everything; edit: anything but the text), push sends only the text of
someone else's note, and their notes stay out of trash, reminders and
reordering. Unlinking drops them.

The Share dialog's calls go to the linked server over the device token, as
Tauri commands and through the FFI. The desktop now offers Share and "Shared
with me"; unlinked, the dialog says sharing needs a server.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

android/ffi/src/lib.rs

@@ -40,11 +40,11 @@ use std::sync::Arc;
 
 use inkwell_core::local::{self, Db};
 use inkwell_core::sync::blobs::BlobStore;
-use inkwell_core::sync::{client, compat, engine, push, state};
+use inkwell_core::sync::{client, compat, engine, push, sharing, state};
 
 use models::{
-    patch_from, BodyItem, BodyTag, ClientUpdate, Identity, Label, Note, NoteDraft, NoteEdit,
-    NoteQuery, ProbeResult, RevokeOutcome, SyncOutcome, SyncStatus,
+    patch_from, BodyItem, BodyTag, ClientUpdate, Identity, Label, Member, Note, NoteDraft,
+    NoteEdit, NoteQuery, NoteShare, ProbeResult, RevokeOutcome, SyncOutcome, SyncStatus,
 };
 
 uniffi::setup_scaffolding!();
@@ -606,6 +606,55 @@ impl Inkwell {
             .map(SyncOutcome::from)
             .map_err(CoreError::network)
     }
+
+    // ──────────────────────────────  sharing  ──────────────────────────────
+    //
+    // The Share dialog asks the server directly (#5175). Unlinked, each answers
+    // `NotLinked`, which the dialog turns into "sharing needs a server".
+
+    /// Everyone on the instance a note can be shared with.
+    pub async fn share_directory(&self) -> Result<Vec<Member>, CoreError> {
+        self.credentials()?;
+        let members = sharing::directory(&self.db)
+            .await
+            .map_err(CoreError::network)?;
+        Ok(members.into_iter().map(Member::from).collect())
+    }
+
+    /// Who this note is shared with.
+    pub async fn note_shares(&self, note_id: String) -> Result<Vec<NoteShare>, CoreError> {
+        self.credentials()?;
+        let shares = sharing::list(&self.db, &note_id)
+            .await
+            .map_err(CoreError::network)?;
+        Ok(shares.into_iter().map(NoteShare::from).collect())
+    }
+
+    /// Share with one member at "view" or "edit", or change their permission.
+    pub async fn share_note(
+        &self,
+        note_id: String,
+        user_id: String,
+        permission: String,
+    ) -> Result<Vec<NoteShare>, CoreError> {
+        self.credentials()?;
+        let shares = sharing::share(&self.db, &note_id, &user_id, &permission)
+            .await
+            .map_err(CoreError::network)?;
+        Ok(shares.into_iter().map(NoteShare::from).collect())
+    }
+
+    pub async fn unshare_note(
+        &self,
+        note_id: String,
+        share_id: String,
+    ) -> Result<Vec<NoteShare>, CoreError> {
+        self.credentials()?;
+        let shares = sharing::unshare(&self.db, &note_id, &share_id)
+            .await
+            .map_err(CoreError::network)?;
+        Ok(shares.into_iter().map(NoteShare::from).collect())
+    }
 }
 
 // ── checklist text, as pure functions ───────────────────────────────────────