Phase 1: Updated compaction.ts
- findCutPoint now returns CutPointResult with isSplitTurn and turnStartIndex
- Can cut at user, assistant, or bashExecution messages (never tool results)
- Added turnPrefixSummary support for split turns (parallel summarization)
- estimateTokens helper for context size estimation
Phase 2: Updated session-manager.ts
- CompactionEntry now has optional turnPrefixSummary field
- loadSessionFromEntries injects both summaries when turn was split
Phase 3: Updated agent-session.ts
- Overflow detection via isContextOverflow after agent_end
- Proactive compaction check on turn_end before next LLM call
- _abortingForCompaction flag to skip saving aborted messages
- Auto-retry after overflow recovery or proactive compaction
- New event fields: reason (overflow/threshold), willRetry
Phase 4: Updated interactive-mode.ts
- Shows reason in compaction status (Context overflow detected...)
- Shows retry status after compaction
Tests updated for new CutPointResult return type.
- Trigger auto-compaction after agent_end instead of during message_end
- Show CompactionComponent after auto-compaction (same as manual /compact)
- Fix cut point to include bash executions before kept user message
- Stop backward scan at compaction, assistant, user, or toolResult boundaries
- Add AgentSessionEvent type extending AgentEvent with auto_compaction_start/end
- Emit events when auto-compaction starts and completes
- TUI shows loader during auto-compaction with escape to cancel
- Rebuilds chat UI when auto-compaction succeeds
