board: a tag in the prose is coloured where it sits, not printed twice

A tagged note was showing its tag twice — once where it was typed, once as a
chip — and the duplicate was the loud copy. Now the chip row carries only what
the body cannot say (a tag lifted off its own line, a label from the picker),
and a `#tag` left mid-sentence is tinted in place.

Which characters are a tag is asked of the CORE, the way the card already asks
it which lines are checklist items: `extract_tag_spans` keeps the spans
`extract_tags` throws away, and `body_tags` hands them to Kotlin. Offsets are
UTF-16 code units, because `AnnotatedString` and JS both index that way and a
char index lands mid-token the first time somebody writes an emoji. The web
keeps its own matcher in markdown.ts, mirroring `line_tags` case for case.

The inline ink is its own table, one Tailwind step deeper than the chip's. A
chip brings its own -100 fill and reads against that alone; inline text sits on
whatever the card is, including a gray-tagged card at neutral-200 — where the
chip's -700 measured 3.98 (green), 4.11 (orange) and 4.34 (teal), under the 4.5
body text needs. At -800/-300 every hue lands 5.63-12.01 light and 7.20-10.84
dark across every palette and generated fill.

Chips now carry the `#` on every surface. The via_tag branch that used to
decide it is gone from the card, and Android's row said no hash at all.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

android/ffi/src/lib.rs

@@ -43,8 +43,8 @@ use thoughtsync_core::sync::blobs::BlobStore;
 use thoughtsync_core::sync::{client, compat, engine, push, state};
 
 use models::{
-    patch_from, BodyItem, ClientUpdate, Identity, Label, Note, NoteDraft, NoteEdit, NoteQuery,
-    ProbeResult, RevokeOutcome, SyncOutcome, SyncStatus,
+    patch_from, BodyItem, BodyTag, ClientUpdate, Identity, Label, Note, NoteDraft, NoteEdit,
+    NoteQuery, ProbeResult, RevokeOutcome, SyncOutcome, SyncStatus,
 };
 
 uniffi::setup_scaffolding!();
@@ -530,6 +530,21 @@ pub fn checklist_items(body: String) -> Vec<BodyItem> {
         .collect()
 }
 
+/// Every `#tag` in a body, with the line and the UTF-16 span each one occupies — so
+/// a card can colour the tag where it was typed instead of printing it twice.
+///
+/// The same argument as `checklist_items` above, and the same answer: the grammar for
+/// what a `#tag` is already exists in Rust, Python and TypeScript. Matching it a
+/// fourth time in Compose would be a fourth place for a tag to change shape when it
+/// syncs — and this one would fail silently, as the wrong characters tinted.
+#[uniffi::export]
+pub fn body_tags(body: String) -> Vec<BodyTag> {
+    local::derive::extract_tag_spans(&body)
+        .into_iter()
+        .map(BodyTag::from)
+        .collect()
+}
+
 /// Helpers, deliberately NOT exported — uniffi only binds what an `#[uniffi::export]`
 /// block names, so these stay Rust-side.
 impl ThoughtSync {

android/ffi/src/models.rs

@@ -76,6 +76,36 @@ impl From<thoughtsync_core::local::derive::DerivedItem> for BodyItem {
     }
 }
 
+/// One `#tag` and where it sits in a note's body.
+///
+/// Mirrors `derive::DerivedTag`. The card colours the tag where it was typed rather
+/// than repeating it as a chip, so it needs the SPAN — and the offsets are UTF-16
+/// code units precisely because Kotlin's `AnnotatedString` counts that way.
+#[derive(Debug, Clone, uniffi::Record)]
+pub struct BodyTag {
+    pub line: u32,
+    pub start: u32,
+    pub end: u32,
+    pub name: String,
+}
+
+impl From<thoughtsync_core::local::derive::DerivedTag> for BodyTag {
+    fn from(t: thoughtsync_core::local::derive::DerivedTag) -> Self {
+        let thoughtsync_core::local::derive::DerivedTag {
+            line,
+            start,
+            end,
+            name,
+        } = t;
+        BodyTag {
+            line,
+            start,
+            end,
+            name,
+        }
+    }
+}
+
 /// An Android build the linked server is offering, already judged to be newer.
 ///
 /// A mirror rather than a re-export of `client::ClientRelease`, for the same