Cut changelog for 0.2.104

[TheGreatAxios]

Summary

• Rename Unreleased to 0.2.104 and fill in the PRs that landed on main after 0.2.103.
• Covers TUI, tools, sub-agents, providers, and the CI required-check split.
• Compaction quality (Compaction preserves the loop and drops the substance #544) stays out of this cut.

Verification

• Changelog-only. Required checks should stay green.

Test plan

• Notes match merged PRs Omit Codex Responses reasoning.summary auto for Terra/Luna #532–Set prompt_cache_key on the Grok and OpenAI Responses adapters #543, Proxy Codex apply_patch onto Corbits file tools #505, Retarget Codex developer bridge for proxy tools #527, Paint live agents above the prompt #534, Split prettier/eslint CI jobs, unmask lint caches, require checks to merge #537
• Compaction preserves the loop and drops the substance #544 not mentioned