chore: prepare 0.12.9 desktop release

Record the approved bilingual notes for todo source entries, accurate
request status, parallel OpenCode reliability, image editing, native
questions, longer Continue requests, reasoning formatting, and activity
history notices. Keep all previously published release entries intact.

Synchronize package and feature-matrix versions for the standard six-target
desktop release. Agent remains 0.11.21; no Agent release or LoongArch preview
is included. Release tags remain pending exact-commit approval and CI.

Validation: 3618 tests passed, 61 skipped; typecheck, lint, and bilingual
release-note verification passed. No local production package was built.

FEATURES.md

@@ -21,7 +21,7 @@ otherwise.
   packages target compatible x64 and arm64 environments, including UOS, Kylin,
   Hygon, Zhaoxin, Kunpeng, and Phytium systems. This is not vendor certification.
   LoongArch has a separate experimental loong64 preview outside standard
-  releases and automatic updates; no preview is planned for 0.12.8. See the
+  releases and automatic updates; no preview is planned for 0.12.9. See the
   [preview boundaries](./docs/development/loongarch-preview-build.md).
 - [x] **Configurable global shortcut**: Enable, disable, or record an Electron
   accelerator under Platform Features / General. The default remains
@@ -174,7 +174,7 @@ otherwise.
   failure, Agent `SIGKILL`/restart, and recovery from a reopened Desktop SQLite
   database. Successful tool START/END events appear exactly once, with no
   Prompt, provider, or tool replay observed. The current Agent source lock is
-  `0.11.21`, while the current Desktop release candidate is `0.12.8`; formal
+  `0.11.21`, while the current Desktop release candidate is `0.12.9`; formal
   publication status follows the separate Agent and Desktop
   release channels. Current macOS source has passed native package installation,
   detached lifecycle, Attach, real Ask/Execute, and cancellation of tools in