Add changelog and release command

- Add CHANGELOG.md with version history
- Add changelog page to docs site
- Add /release command for preparing releases

.claude/commands/release.md

@@ -0,0 +1,61 @@
+# Release
+
+Prepare a new release for cmuxterm. This command updates the changelog, bumps the version, and creates a release tag.
+
+## Steps
+
+1. **Determine the new version number**
+   - Get the current version from `GhosttyTabs.xcodeproj/project.pbxproj` (look for `MARKETING_VERSION`)
+   - Bump the minor version unless the user specifies otherwise (e.g., 1.12.0 → 1.13.0)
+
+2. **Gather changes since the last release**
+   - Find the most recent git tag: `git describe --tags --abbrev=0`
+   - Get commits since that tag: `git log --oneline <last-tag>..HEAD --no-merges`
+   - Categorize changes into: Added, Changed, Fixed, Removed
+
+3. **Update the changelog**
+   - Add a new section at the top of `CHANGELOG.md` with the new version and today's date
+   - Write clear, user-facing descriptions (not raw commit messages)
+   - Focus on what matters to users: new features, bug fixes, breaking changes
+   - Also update `docs-site/content/docs/changelog.mdx` with the same content
+
+4. **Bump the version in Xcode project**
+   - Update all occurrences of `MARKETING_VERSION` in `GhosttyTabs.xcodeproj/project.pbxproj`
+   - There are typically 4 occurrences (Debug/Release for main app and CLI)
+
+5. **Commit the changes**
+   - Stage: `CHANGELOG.md`, `docs-site/content/docs/changelog.mdx`, `GhosttyTabs.xcodeproj/project.pbxproj`
+   - Commit message: `Bump version to X.Y.Z`
+
+6. **Create and push the tag**
+   - Create tag: `git tag vX.Y.Z`
+   - Push commits: `git push origin main`
+   - Push tag: `git push origin vX.Y.Z`
+
+7. **Monitor the release**
+   - Watch the workflow: `gh run watch --repo manaflow-ai/cmuxterm`
+   - Verify the release appears at: https://github.com/manaflow-ai/cmuxterm/releases
+
+## Changelog Guidelines
+
+- Use present tense ("Add feature" not "Added feature")
+- Group by category: Added, Changed, Fixed, Removed
+- Be concise but descriptive
+- Focus on user impact, not implementation details
+- Link to issues/PRs if relevant
+
+## Example Changelog Entry
+
+```markdown
+## [1.13.0] - 2025-01-30
+
+### Added
+- New keyboard shortcut for quick tab switching
+
+### Fixed
+- Memory leak when closing split panes
+- Notification badges not clearing properly
+
+### Changed
+- Improved terminal rendering performance
+```