Session Summaries That Survive Compaction

PROJECT CONTEXT:
Compaction and restarts keep eating knowledge my agent already earned: what worked, what failed, what the user prefers. Memory research calls compaction the moment memories die - unless you write summaries designed to survive it.

GOAL:
Add a durable session-summary layer: written at session end and before compaction, stored outside the context, and reloaded into future sessions.

REQUIREMENTS:
- A session summary written to disk at session end and immediately before every compaction
- Summary content: outcomes, working commands, failed approaches, user preferences, project facts
- Summaries stored per project, outside the conversation context
- New sessions load the latest summary (or a digest of recent ones) at start
- A size cap with oldest-first pruning so the store stays lean

CONSTRAINTS:
- Summaries capture durable knowledge, not conversational blow-by-blow
- Failed approaches are first-class content - they prevent repeated mistakes

DEFINITION OF DONE:
- Killing a session and starting fresh, the agent knows the project state and past decisions
- A previously-failed approach is not retried blindly in a new session
- Summary files stay under the size cap across 10+ sessions
- Pre-compaction summaries capture the about-to-be-compacted knowledge

COMMON FAILURES TO AVOID:
- Summaries written only on clean exit, so crashes lose everything
- Transcript-shaped summaries that are as long as what they summarize
- Never loading the summaries back, making the whole layer decorative
- Unbounded accumulation until the summary store itself needs compaction