P4b: skill noun + contrib/store (SQLite for budget/persona/skill/audit)

Merges the skill half of the persona/skill pair plus the second nested module.
(Squashed onto main from phase-4b-skill; the audit/budget/persona batteries it
was stacked on already landed via the P4 merge.)

- skill/: clean-redesign Skill noun + LEAN SkillStore (lifecycle/versions/
  schedule only) + ToRunnable + Memory default.
- contrib/store/: separate go.mod carrying modernc.org/sqlite, so the driver
  never enters the core go.sum. db.Budget()/Personas()/Skills()/Audit() back
  all four store seams (JSON-blob + indexed columns; round-trip tested).
  Includes the verified gadfly #5 fixes (AppendVersion tx+UNIQUE+error,
  Mark*ScheduledRun atomic json_set, busy_timeout, NaN guard).
- CI: builds + tests the nested module and asserts it owns the sqlite driver.

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

CLAUDE.md

@@ -58,30 +58,42 @@ CORE (majordomo + stdlib):
              structured output — no separate structured/ pkg)
   llmmeta/  shared meta-LLM helper over model/            [P1 ✓]
   compact/  context compactor (WithCompactor hook)       [P2 ✓]
-  tools/    generic tool library: Register (think/now/    [P3 wip]
+  tools/    generic tool library: Register (think/now/    [P3 ✓]
             cite, zero-config) + RegisterMeta (classify/
             extract_entities/summarize) + RegisterStore
             (kv_*/file_*, default static quota); seams in
             research_providers.go/file_storage.go/
             kv_storage.go/quota_provider.go. End-to-end
-            "agent calls a tool" test green. Remaining:
-            web/net/compose groups + default backends     [P3]
+            "agent calls a tool" test green. Remaining
+            (deferred): web/net/compose groups + backends
 
 BATTERIES (opt-in siblings, each nil-safe + a default):
-  persona/   Agent noun + Storage seam + builtin loader [P4 ~]
+  persona/   Agent noun + Storage seam + builtin loader [P4 ✓]
              + ToRunnable() bridge to run.RunnableAgent +
              Memory default (host: chatbot/commands/personalization)
-  skill/     rich Skill + SkillStore seam + toml loader  [P4]
+  skill/     Skill noun + LEAN SkillStore (lifecycle/    [P4 ✓]
+             versions/schedule, NOT mort's 60-method
+             monster) + ToRunnable + Memory default
   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]
+  critic/    two-tier timeout watchdog (run.Critic) +    [P4 ✓]
+             Escalator policy seam + ExtendOnce default
+  schedule/  generic cron Runner (Tick/Loop over a wired [P4 ✓]
+             Due/Run/Mark/Next; no cron grammar of its own)
+  checkpoint/ CheckpointStore + run.Checkpointer handle  [P4 ✓]
+             (throttled Save/Complete/Fail) + Memory
   budget/    DBBudget rolling-7d + NoOp (run.Budget);    [P4 ✓]
              BudgetStorage iface + Memory default
 
-contrib/store/   SECOND module (+ modernc.org/sqlite):   [P4]
-  in-memory + pure-Go SQLite impls of every *Store seam
+contrib/store/   SECOND module (+ modernc.org/sqlite):   [P4 ✓]
+  pure-Go SQLite impls of ALL store seams: budget +
+  persona + skill + audit (JSON-blob+indexed cols,
+  round-trip tested). CI proves the driver lands HERE,
+  not in the core go.sum.
+
+NOTE: critic/checkpoint executor wiring (run.Ports.Critic /
+.Checkpointer call sites) is a P2 follow-up — the batteries +
+defaults exist ahead of that wiring.
 ```
 
 ### The one architectural move