feat(changelog): one source file per release, generated outputs

Release notes now live in changelog/<version>.md (front matter with
version and date, then ## App and ## VS Code sections grouped into
New, Improvements, Fixes, Misc) plus changelog/unreleased.md for what
has not shipped. `bun run changelog:build` renders CHANGELOG.md,
packages/vscode/CHANGELOG.md, and changelog/index.json from them;
`changelog:check` fails when the outputs are behind and runs in CI and
in release:prepare. `oc-dev create-release` promotes unreleased.md to
the versioned file dated today and rebuilds.

The existing history was split mechanically: every bullet kept, sorted
into groups by keyword, five hand-typed headers with one-digit days
normalised to YYYY-MM-DD (the update dialog matched none of them). The
generated files keep today's release headers, which the update dialog,
the release workflow, and the website match by regex.

Claude-Session: https://claude.ai/code/session_01VqV56Hez25hTxXH4ipJfzH

changelog/1.8.5.md

@@ -0,0 +1,31 @@
+---
+version: 1.8.5
+date: 2026-03-04
+---
+
+## App
+
+### Improvements
+- Desktop: startup now opens the app shell much earlier while background services continue loading.
+- VSCode: edit-style tool results now open directly in a focused diff view.
+- UI/Theming: unified loading logos and startup screens across runtimes, with visuals that better match your active theme.
+- Projects/UI: project icons now follow active theme foreground colors consistently.
+- Reliability: improved early startup recovery.
+- Mobile/PWA: respected OS rotation lock by removing forced orientation behavior in the web app shell (thanks to @theluckystrike).
+
+### Fixes
+- Desktop/macOS: fixed early title updates that could shift traffic-light window controls on startup.
+- VSCode: cleaned up extension settings by removing duplicate display controls and hiding sections that do not apply in the editor environment.
+- Chat: fixed focus-mode composer layout.
+- Tunnel/CLI: fixed one-time Cloudflare tunnel connect links in CLI output for `--try-cf-tunnel` (thanks to @plfavreau).
+
+## VS Code
+
+### Improvements
+- Chat/Files: edit-style tool results now open in a VS Code diff editor with focus on the first changed line.
+- Chat: improved focus-mode input layout.
+- UI/Theming: aligned startup/loading branding with the active theme for a more consistent look during connection and auth states.
+- Reliability: improved startup recovery for provider/model/agent loading.
+
+### Fixes
+- Settings: removed duplicate chat display options from Appearance and hid extension-irrelevant sections.