Session memory extraction + tiered context loading improvements

- /review-all-gdds, /architecture-review, /story-done: auto-append Session
  Extract block to active.md after report write (verdict, flags, next action)
- /review-all-gdds, /architecture-review, /create-epics-stories, /content-audit:
  L0 summary scan phase before full document load (reduces token cost)
- GDD template: added Summary section + Cross-References table + Last Verified field
- ADR template: added Summary section + Last Verified field

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/docs/templates/architecture-decision-record.md

@@ -6,12 +6,25 @@
 
 ## Date
 
-[YYYY-MM-DD]
+[YYYY-MM-DD — when this ADR was written]
+
+## Last Verified
+
+[YYYY-MM-DD — when this ADR was last confirmed accurate against the current
+engine version and design. Update this date when you re-read and confirm it
+is still correct, even if nothing changed.]
 
 ## Decision Makers
 
 [Who was involved in this decision]
 
+## Summary
+
+[2 sentences: what problem this ADR solves, and what was decided. Written for
+tiered context loading — a skill scanning 20 ADRs uses this to decide whether
+to read the full decision. Be specific: name the system, the problem, and the
+chosen approach.]
+
 ## Engine Compatibility
 
 | Field | Value |