core: extract the store and sync engine into a shared crate (M12 step 1)

Android becomes a native Kotlin client over this same code (Scribe note 2730), so
the local store and sync engine stop being modules of the desktop app and become
`thoughtsync-core`, a crate with no UI framework in it at all.

This is a move, not a rewrite, and the measurement is why: every file in local/
and sync/ already carried ZERO Tauri references — 4,980 of 6,372 lines. The
coupling was 473 lines of command shim, which stays behind in the desktop crate
as src/commands/. Kept as git renames so history follows the files.

The desktop imports them under their old names (`use thoughtsync_core::{local,
sync}`) so every call site reads exactly as before. What moved is where they
live, not what they are.

Two things a workspace changes that are easy to miss, both caught before pushing:

[profile.release] now lives at the workspace ROOT. Cargo silently ignores
profiles declared by a non-root member — leaving it in the desktop crate would
have dropped lto/strip/opt-level from every release build with only a warning.

And a workspace shares ONE target dir, so the bundles moved from
desktop/src-tauri/target to target/. Thirteen references across publish-release,
debundle-graphics, verify.sh, package-prebuilt and the workflow now point there.
Pinning target-dir back would have been the smaller diff, but the Android lane
also produces Rust artifacts and they do not belong under desktop/.

Also retires the Tauri Android lane in the same push rather than leaving a path
that is being replaced: gen/android, android.yml and docs/android-dev.md are
gone, the mobile_entry_point attribute with them, and the lib drops to rlib —
staticlib/cdylib existed for Tauri mobile, and the .so Android loads will be
built from the core crate instead. Rule 22, no parallel path.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

core/src/sync/wire.rs

@@ -0,0 +1,166 @@
+//! The delta-feed JSON shapes, exactly as `GET /api/sync/changes` sends them.
+//!
+//! Mirrors the server's serializers (`notes/serialize.py` + `serialize.py`) — see
+//! `docs/sync.md` for the contract. Every field is `#[serde(default)]` or `Option`
+//! so a NEWER server adding fields, or an older one omitting one, degrades to a
+//! partial note rather than failing the whole page. Losing one attribute is
+//! recoverable; refusing a page stalls sync permanently at that cursor.
+
+use serde::Deserialize;
+
+#[derive(Debug, Clone, Deserialize, Default)]
+pub struct ChangesPage {
+    #[serde(default)]
+    pub notes: Vec<Note>,
+    #[serde(default)]
+    pub labels: Vec<Label>,
+    #[serde(default)]
+    pub cursor: i64,
+    #[serde(default)]
+    pub has_more: bool,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+pub struct Note {
+    pub id: String,
+    #[serde(default)]
+    pub title: Option<String>,
+    #[serde(default)]
+    pub body: String,
+    #[serde(default = "default_color")]
+    pub color: String,
+    #[serde(default = "default_kind")]
+    pub kind: String,
+    #[serde(default)]
+    pub position: i64,
+    #[serde(default)]
+    pub pinned: bool,
+    #[serde(default)]
+    pub archived: bool,
+    /// The server derives this from `deleted_at` — trash, NOT a tombstone.
+    #[serde(default)]
+    pub trashed: bool,
+    /// WHEN it was trashed. The trash-retention clock runs from here, so it has to be
+    /// the server's timestamp rather than anything this device invents. Absent from an
+    /// older server, which is why it's optional rather than required.
+    #[serde(default)]
+    pub deleted_at: Option<String>,
+    #[serde(default)]
+    pub remind_at: Option<String>,
+    #[serde(default)]
+    pub recurrence: Option<String>,
+    #[serde(default)]
+    pub created_at: Option<String>,
+    #[serde(default)]
+    pub updated_at: Option<String>,
+    #[serde(default)]
+    pub sync_revision: i64,
+    /// Set means the row was permanently purged: a content-less tombstone whose only
+    /// job is to tell clients to delete their copy.
+    #[serde(default)]
+    pub purged_at: Option<String>,
+    #[serde(default)]
+    pub labels: Vec<NoteLabel>,
+    #[serde(default)]
+    pub items: Vec<Item>,
+    #[serde(default)]
+    pub attachments: Vec<Attachment>,
+    #[serde(default)]
+    pub previews: Vec<Preview>,
+}
+
+impl Note {
+    pub fn is_tombstone(&self) -> bool {
+        self.purged_at.is_some()
+    }
+}
+
+/// A label as it appears attached to a note. Carries enough to materialize the label
+/// row itself, which is what lets a membership be applied even if the label's own
+/// delta hasn't arrived (see `pull::apply_page`).
+#[derive(Debug, Clone, Deserialize)]
+pub struct NoteLabel {
+    pub id: String,
+    #[serde(default)]
+    pub name: String,
+    #[serde(default = "default_color")]
+    pub color: String,
+    /// True when the membership came from a `#tag` in the body rather than a manual
+    /// assignment. Applied verbatim rather than re-derived — see `pull::apply_page`.
+    #[serde(default)]
+    pub via_tag: bool,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+pub struct Item {
+    pub id: String,
+    #[serde(default)]
+    pub text: String,
+    #[serde(default)]
+    pub checked: bool,
+    #[serde(default)]
+    pub position: i64,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+pub struct Attachment {
+    pub id: String,
+    #[serde(default)]
+    pub url: String,
+    #[serde(default)]
+    pub filename: Option<String>,
+    #[serde(default = "default_mime")]
+    pub mime: String,
+    #[serde(default)]
+    pub size: Option<i64>,
+    #[serde(default)]
+    pub sha256: Option<String>,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+pub struct Preview {
+    pub id: String,
+    #[serde(default)]
+    pub url: String,
+    #[serde(default)]
+    pub title: Option<String>,
+    #[serde(default)]
+    pub description: Option<String>,
+    #[serde(default)]
+    pub image_url: Option<String>,
+    #[serde(default)]
+    pub site_name: Option<String>,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+pub struct Label {
+    pub id: String,
+    #[serde(default)]
+    pub name: String,
+    #[serde(default = "default_color")]
+    pub color: String,
+    #[serde(default)]
+    pub sync_revision: i64,
+    #[serde(default)]
+    pub purged_at: Option<String>,
+    #[serde(default)]
+    pub created_at: Option<String>,
+}
+
+impl Label {
+    pub fn is_tombstone(&self) -> bool {
+        self.purged_at.is_some()
+    }
+}
+
+fn default_color() -> String {
+    "default".to_string()
+}
+
+fn default_kind() -> String {
+    "text".to_string()
+}
+
+fn default_mime() -> String {
+    "application/octet-stream".to_string()
+}