P4: audit battery — run.Audit Sink + Writer + queryable Memory store

First Tier-2 battery, plugging into run.Ports.Audit:
- storage.go/writer.go: skillaudit's Storage interface + per-run Writer moved
  clean (only utils->fmt); the Writer already matches run.RunRecorder's shape.
- sink.go: Sink adapts a Storage to run.Audit (StartRun -> a run row + a Writer
  wrapped as run.RunRecorder, converting run.RunStats on Close). NewSink(nil) is
  equivalent to no audit. Compile-time proofs: Sink is run.Audit, recorder is
  run.RunRecorder.
- memory.go: NewMemory() — a zero-dependency, queryable in-process Storage
  (retains runs + logs; all 17 read/filter/purge/walk methods) so a light host
  gets run history with no setup. Mort keeps its GORM Storage; contrib/store
  adds durable SQLite at P4.

End-to-end test: wire audit.NewSink(audit.NewMemory()) into the executor, run an
agent, and the run is recorded with terminal status/output and queryable by
caller. CI invariant verified: core imports ZERO from the audit battery (proper
battery direction; battery imports core, never the reverse).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -70,7 +70,8 @@ CORE (majordomo + stdlib):
 BATTERIES (opt-in siblings, each nil-safe + a default):
   persona/   Agent noun + AgentStore seam + yml loader   [P4]
   skill/     rich Skill + SkillStore seam + toml loader  [P4]
-  audit/     run-trace Sink (+ Noop/Slog)                [P4]
+  audit/     run.Audit Sink + Writer + queryable Memory  [P4 ✓]
+             default (skillaudit Storage iface; GORM stays in mort)
   critic/    two-tier timeout state machine + Escalator  [P4]
   schedule/  cron runner cores                           [P4]
   checkpoint/ durable resume seam                        [P4]