One tag-name fold on the web and on Android, beside the core's (#5373, #5385)

The web compared or keyed tag names with name.toLowerCase() at five sites:
the labels store's merge check, LabelPicker's create check, NoteCard's
colour map, and colors.ts twice. Android had three, plus TagsScreen's rename
dialog using equals(ignoreCase = true). Each now calls foldTag(name), which
says what the core's derive::fold and the server's labeling.named say.

Android's rename dialog now predicts a merge the same way the core decides
one. Per-character ignoreCase and full lowercasing disagree on letters like
İ, whose lowercase is two characters. LabelPicker's search filter keeps
its own lowercasing: that is search, not identity.

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

android/app/src/main/java/com/fabledsword/inkwell/ui/DerivedTint.kt

@@ -86,9 +86,9 @@ fun derivedTint(id: String): String {
  * Deriving has no mint points to miss and no backfill for the tags already out there.
  * The cost is that renaming a tag recolours it, which is fair: the name IS the tag.
  *
- * Lowercased because tags dedupe case-insensitively — `#Todo` renamed to `#todo` is
- * the same tag and should not change colour. Kotlin's `lowercase()` and the web's
- * `toLowerCase()` are both locale-independent, so the mirror holds.
+ * Folded because `#Todo` renamed to `#todo` is the same tag and should not change
+ * colour. [foldTag] and the web's are both locale-independent lowercasing, so the
+ * mirror holds.
  */
 fun resolvedLabelColor(
     name: String,
@@ -98,5 +98,12 @@ fun resolvedLabelColor(
     when {
         color.isNotEmpty() && color != "default" && color in known -> color
         name.isEmpty() -> "default"
-        else -> derivedTint(name.lowercase())
+        else -> derivedTint(foldTag(name))
     }
+
+/**
+ * How two tag names compare: equal once every letter is lowercased, accented ones
+ * included, so `#Café` and `#CAFÉ` are one tag. The core's `derive::fold`, the server's
+ * `labeling.named` and the web's `foldTag` fold the same way (#5385).
+ */
+fun foldTag(name: String): String = name.lowercase()

android/app/src/main/java/com/fabledsword/inkwell/ui/NoteCard.kt

@@ -366,11 +366,11 @@ private fun tintTags(
             // A tag the note does not carry as a label yet — just typed, not yet
             // derived — still gets a colour: `labelTint` falls back to deriving one
             // from the name, which is what the chip would have shown anyway.
-            val picked = note.labels.associate { it.name.lowercase() to it.color }
+            val picked = note.labels.associate { foldTag(it.name) to it.color }
             buildAnnotatedString {
                 append(text)
                 spans.forEach { tag ->
-                    val tint = labelTint(tag.name, picked[tag.name.lowercase()].orEmpty())
+                    val tint = labelTint(tag.name, picked[foldTag(tag.name)].orEmpty())
                     addStyle(
                         SpanStyle(color = tint.tagInk(dark), fontWeight = FontWeight.Medium),
                         tag.start.toInt(),

android/app/src/main/java/com/fabledsword/inkwell/ui/TagsScreen.kt

@@ -401,7 +401,7 @@ private fun RenameDialog(
     var text by remember(tag.id) { mutableStateOf(tag.name) }
     val trimmed = text.trim()
     val clash =
-        others.firstOrNull { it.id != tag.id && it.name.equals(trimmed, ignoreCase = true) }
+        others.firstOrNull { it.id != tag.id && foldTag(it.name) == foldTag(trimmed) }
     val submit = {
         when {
             trimmed.isEmpty() -> Unit