chore: move changelog entry and update CLAUDE.md guidelines

Move #880 changelog entry to bottom of Added section. Update CLAUDE.md
to note that new changelog entries should be placed at the bottom of
their section.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: brendan-kellam

CHANGELOG.md

@@ -8,8 +8,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
-- Added `install_id` to PostHog event properties. [#880](https://github.com/sourcebot-dev/sourcebot/pull/880)
 - Added PostHog events for repo index job success/failure and code host type to connection sync events. [#878](https://github.com/sourcebot-dev/sourcebot/pull/878)
+- Added `install_id` to PostHog event properties. [#880](https://github.com/sourcebot-dev/sourcebot/pull/880)
 
 ### Changed
 - Changed the me-control to render the user's avatar in the top-bar. [#874](https://github.com/sourcebot-dev/sourcebot/pull/874)

CLAUDE.md

@@ -45,5 +45,5 @@ PR description:
 - If a GitHub issue number was provided, include `Fixes #<github_issue_number>` in the PR description
 
 After the PR is created:
-- Update CHANGELOG.md with an entry under `[Unreleased]` linking to the new PR
+- Update CHANGELOG.md with an entry under `[Unreleased]` linking to the new PR. New entries should be placed at the bottom of their section.
 - If the change touches `packages/mcp`, update `packages/mcp/CHANGELOG.md` instead