- Updated compaction, branch summarization, and session dump formatting to pass preferred model tool syntax into conversation serialization.
- Enhanced shared serializers to render assistant tool calls and tool results through grammar envelopes when syntax is available, with the prior compact format as fallback.
- Aligned prompt, preview, and test fixtures to the new transcript tags: `[Think]`, `[Tool Call]`, and `[Tool Result]`.
- Relocated compaction, branch-summarization, pruning, and utils from coding-agent to packages/agent/src/compaction.
- Moved OpenAI remote compaction helpers from packages/ai to the new compaction module.
- Added handoff.ts with extractHandoffDocument, createHandoffContext, and renderHandoffPrompt helpers.
- Exposed new entries.ts with standalone SessionEntry types so coding-agent no longer owns them.