rename: the desktop is Inkwell — crates, Tauri identity, data move, packaging

Step 3 of milestone 481 (Scribe note 5071: a full rename).

- crates thoughtsync-{core,desktop,ffi,uniffi-bindgen} → inkwell-*, the
  Cargo.lock entries moved to match (checked with `cargo metadata --locked`)
- Tauri: productName "Inkwell", identifier com.fabledsword.inkwell, binary
  `inkwell`, updater feed on bvandeusen/inkwell, store file inkwell.db
- client agent inkwell-desktop, headers X-Inkwell-Client/-Protocol (the server
  reads neither), capture event inkwell://captured, display-version env
- .deb: conflicts + replaces thought-sync, so the updater's install retires the
  old package instead of colliding on it. kebab-case("Inkwell") is `inkwell`, so
  the package name finally matches the command and verify.sh now asserts it
- pacman: inkwell, conflicting with and replacing thoughtsync and
  thoughtsync-desktop
- AppImage ~/Applications/Inkwell.AppImage, menu entry inkwell.desktop,
  installer, release titles, desktop asset names in fetch-clients.sh

The one shim, chosen by the operator because it is the only copy of a
local-first user's notes: crossover.rs moves the old
com.fabledsword.thoughtsync app-data dir's contents into the new one on startup,
before the store opens, renaming thoughtsync.db and its -wal/-shm with it. It
skips when the new dir already has a store, and anything already in the new dir
wins (the installer writes its channel marker there first). Tested.

Android's Kotlin side (package, applicationId, uniffi class) is step 4. Its
release asset names stay thoughtsync.* until then.

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

desktop/src-tauri/src/update.rs

@@ -12,7 +12,7 @@
 //! is the whole point of the change. NOTHING HERE MOVED: this code only ever read
 //! `<channel>/latest.json`, and that is still where the manifest lands.
 //!
-//! The feed lives on Fabled-Git rather than on a ThoughtSync server, deliberately:
+//! The feed lives on Fabled-Git rather than on an Inkwell server, deliberately:
 //! this app is usable having never linked a server, and an install that can't reach
 //! its own updates because it isn't paired with anything would contradict the whole
 //! local-first premise.
@@ -27,10 +27,10 @@ use serde::{Deserialize, Serialize};
 use tauri::State;
 use tauri_plugin_updater::UpdaterExt;
 
-use thoughtsync_core::local::{store, Db};
+use inkwell_core::local::{store, Db};
 
 /// Where the manifests live. Fixed tags, so these URLs are permanent.
-const FEED_BASE: &str = "https://git.fabledsword.com/bvandeusen/thoughtsync/releases/download";
+const FEED_BASE: &str = "https://git.fabledsword.com/bvandeusen/inkwell/releases/download";
 
 const CHANNEL_PREF: &str = "update_channel";
 
@@ -330,7 +330,7 @@ mod tests {
     use std::sync::atomic::{AtomicU32, Ordering};
 
     fn db() -> Db {
-        thoughtsync_core::local::open_in_memory().expect("in-memory db")
+        inkwell_core::local::open_in_memory().expect("in-memory db")
     }
 
     /// A scratch path nothing else will collide with. Process id keeps concurrent