feat(dictionary): add iCloud KVS sync, cloud ASR, and lexicon expansion

Mirror the personal dictionary through iCloud Key-Value Store with
deterministic merge rules, main-app-only sync UI, and App Group as the
keyboard runtime cache. Add cloud-engine ASR with dictionary bias and
expand the bundled custom language model lexicon.

docs/personal-dictionary-icloud-kvs-checklist.md

@@ -0,0 +1,28 @@
+# Personal Dictionary iCloud KVS — Manual Verification Checklist
+
+Use this on **macOS with Xcode 16+** and at least two devices signed into the **same Apple ID** with iCloud Drive / iCloud enabled.
+
+## Prerequisites
+
+1. In Apple Developer Portal, enable **iCloud** → **Key-value storage** for `com.osgkeyboard.ios`.
+2. Regenerate provisioning profiles after entitlements change.
+3. Run `xcodegen generate` and install a fresh build on each device.
+
+## Scenarios
+
+| # | Steps | Expected |
+|---|--------|----------|
+| 1 | Device A: open Personal Dictionary, enable **Sync via iCloud**, add term `TestWordA` | Toggle stays on; term appears locally |
+| 2 | Device B: open app → Personal Dictionary tab | `TestWordA` appears after pull (may take up to ~1 min) |
+| 3 | Device B: add `TestWordB` | Device A eventually shows both terms |
+| 4 | Both devices: edit same term offline, then go online | Newer edit wins; aliases union when terms match |
+| 5 | Device A: delete a term | Term disappears on Device B after sync |
+| 6 | Device A: disable iCloud sync | Local dictionary remains; Device B stops receiving new edits from A |
+| 7 | Sign out of iCloud on one device | App keeps local dictionary; sync errors may surface in UI |
+| 8 | Keyboard extension on Device A | Uses App Group cache immediately after main-app save — no iCloud wait |
+
+## Notes
+
+- KVS propagation is **eventual**; force-quit and reopen the app to speed up pulls.
+- The keyboard extension never talks to iCloud directly; only the main app syncs.
+- Payload limit is ~1 MB per key; very large dictionaries should show the “too large” error.