v0.58.8 — Archive sessions on /new, fix deepsearch test

Features

• archive sessions on /new instead of deleting + fix deepsearch test

Documentation

• reverse CHANGELOG order to newest-first
• regenerate full CHANGELOG.md from git history via generate-changelog.sh
• deprecate manual changelog edits — point to generate-changelog.sh

Infrastructure

• add generate-changelog.sh — conventional-commit changelog generator

Full Changelog: v0.58.7...v0.58.8