feat(new): harden skill revisions

AgentCompany-New/src/main/database/migrations/007-skill-hardening.ts

@@ -0,0 +1,4 @@
+export const skillHardeningSchema = `
+  create unique index if not exists idx_skill_runtime_snapshots_agent_run
+    on skill_runtime_snapshots(agent_id, run_id);
+`;