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/1.13.3.md

@@ -0,0 +1,50 @@
+---
+version: 1.13.3
+date: 2026-06-24
+---
+
+## App
+
+### New
+- Git: Git identities can now enable SSH commit signing.
+
+### Improvements
+- Chat: selecting a user-installed skill from the slash command menu now invokes the skill instead of inserting the skill name as plain text (thanks to @IbrahimKhan12).
+- Chat: code blocks in user messages now preserve characters like `<` and `->` instead of escaping them inside the code block (thanks to @bashrusakh).
+- Chat: Arrow Up opens prompt history again when the cursor is at the start of the composer.
+- Agents: agent settings now include thinking variant, temperature, and top-p controls, and clearing temperature or top-p now removes the override (thanks to @bashrusakh).
+- Settings/Models: per-model visibility and sibling model selections now stay saved after changes (thanks to @attilaszasz).
+- Settings/Skills: the skills catalog refreshes after catalog settings change (thanks to @gokulkgm).
+- Providers: disconnecting a provider from settings now works for the selected provider (thanks to @bashrusakh).
+- Git: pushing from the Git view now syncs first, reducing rejected pushes when the branch needs to update.
+- Usage: MiniMax M3 and Token Plan usage now handle the provider's latest API response format (thanks to @baruchvitorino).
+- VSCode: font size and padding preferences now apply inside the extension webview (thanks to @Sin991114).
+- Files: downloads and file names with non-Latin characters now handle those characters correctly in headers (thanks to @FanFan4204).
+
+### Fixes
+- Chat: pasted text containing `@` no longer opens file mention autocomplete unexpectedly (thanks to @charpeni).
+- Chat: switching sessions and loading older messages no longer causes the conversation to jump backward or oscillate around the current scroll position (thanks to @herjarsa).
+- Sessions: new sessions now stay attached to the selected project or current workspace directory instead of sometimes appearing under a stale project (thanks to @bashrusakh).
+- Sessions: pinned sessions and folder rows no longer disappear from the sidebar after an empty session-list refresh (thanks to @bashrusakh).
+- Startup: managed OpenCode server processes left behind by a previous crash are cleaned up on the next start.
+- CLI: stale server PID files are checked more carefully so unrelated processes are not mistaken for an OpenChamber server.
+- Mobile: subagent chevrons no longer overlap long session titles, and session grouping now matches the exact workspace directory (thanks to @weixiang1862, @lilyzhaun).
+
+## VS Code
+
+### Improvements
+- Chat: selecting a user-installed skill from the slash command menu now invokes the skill instead of inserting the skill name as plain text (thanks to @IbrahimKhan12).
+- Chat: code blocks in user messages now preserve characters like `<` and `->` instead of escaping them inside the code block (thanks to @bashrusakh).
+- Chat: Arrow Up opens prompt history again when the cursor is at the start of the composer.
+- Agents: agent settings now include thinking variant, temperature, and top-p controls, and clearing temperature or top-p now removes the override (thanks to @bashrusakh).
+- Settings/Models: per-model visibility and sibling model selections now stay saved after changes (thanks to @attilaszasz).
+- Settings: font size and padding preferences now apply inside the extension webview (thanks to @Sin991114).
+- Settings/Skills: the skills catalog refreshes after catalog settings change (thanks to @gokulkgm).
+- Usage: MiniMax M3 and Token Plan usage now handle the provider's latest API response format (thanks to @baruchvitorino).
+
+### Fixes
+- Chat: pasted text containing `@` no longer opens file mention autocomplete unexpectedly (thanks to @charpeni).
+- Chat: switching sessions and loading older messages no longer causes the conversation to jump backward or oscillate around the current scroll position (thanks to @herjarsa).
+- Sessions: new sessions now stay attached to the selected workspace directory instead of sometimes appearing under a stale project (thanks to @bashrusakh).
+- Sessions: pinned sessions and folder rows no longer disappear from the sidebar after an empty session-list refresh (thanks to @bashrusakh).
+- Startup: managed OpenCode server processes left behind by a previous extension crash are cleaned up on the next start.