Enhancement: Persistent architectural decision memory across sessions

[Delqhi]

Enhancement: Persistent Architectural Decision Memory

Inspired by

Kilo Memory Bank, Oh-My-Pi hindsight agent memory management

What it does

SIN-Code currently records failures (lessons.db) and general memory (MEMORY.md), but does not persistently track architectural decisions across sessions.

Current state

• lessons.db — records verify.fail + tool.error (reactive)
• MEMORY.md — auto-generated workspace/user memory
• instinct — learned instincts with confidence scoring
• Missing: proactive architectural decision recording

Proposed improvements

1. Auto-capture architectural decisions: when agent chooses a pattern/approach, record it
2. Decision record: {timestamp, session, decision, rationale, alternatives, files}
3. Surface relevant past decisions in new sessions (session-start context injection)
4. sin-code memory decisions — list/search architectural decisions
5. Integrate with existing auto_mem package (byte-stable MEMORY.md)

Mandate compliance

• M3: Memory is read-only during verification — does not affect gate
• M7: SQLite store with mutex (existing pattern)

Priority: Low

Effort: Medium