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/1.8.2.md

@@ -0,0 +1,31 @@
+---
+version: 1.8.2
+date: 2026-03-01
+---
+
+## App
+
+### New
+- Chat: added a new "Share as image" action (thanks to @Jovines).
+
+### Improvements
+- Updates: hardened the self-update flow with safer release handling and fallback behavior.
+- Chat: improved message readability with cleaner tool/reasoning rendering and less noisy activity timing in busy conversations (thanks to @nelsonPires5).
+- Desktop/Chat: permission toasts now include session context and a clearer permission preview (thanks to @nelsonPires5).
+- Notifications/Voice: consolidated TTS and summarization service wiring for steady text-to-speech and summary flows (thanks to @nelsonPires5).
+
+### Fixes
+- VSCode: fixed live streaming edge cases for event endpoints with query/trailing-slash variants.
+- Reliability: improved event-stream/session visibility handling when the app is hidden or restored.
+- Windows: fixed CLI/runtime path and spawn edge cases to reduce startup and command failures on Windows (thanks to @plfavreau).
+- Deployment: fixed Docker build/runtime issues (thanks to @nzlov).
+
+## VS Code
+
+### Improvements
+- Chat: improved message readability with cleaner tool/reasoning rendering and more polished markdown presentation in long responses.
+- Chat Activity: timing display is now less noisy, with detailed end timestamps shown on hover when you need them (thanks to @nelsonPires5).
+- Reliability: improved panel visibility/reconnect handling.
+
+### Fixes
+- Reliability: fixed live-streaming edge cases for event endpoints with query/trailing-slash variants.