refactor: restructure project layout and add install.mjs

- Move src/ → plugin/ with subdirectories:
  - plugin/core/ (business logic, models, store, permissions, utils, memory)
  - plugin/tools/ (query, resources)
  - plugin/commands/ (placeholder for slash commands)
  - plugin/hooks/ (placeholder for lifecycle hooks)
  - plugin/index.ts (wiring layer only, no business logic)
- Add install.mjs with --install, --uninstall, --openclaw-profile-path
- Add skills/ and docs/ root directories
- Move planning docs (PLAN.md, FEAT.md, AGENT_TASKS.md) to docs/
- Remove old scripts/install.sh
- Update tsconfig rootDir: src → plugin
- Update README.md and README.zh.md with new layout
- Bump version to 0.2.0
- All tests pass

plugin/core/models/audit.ts

@@ -0,0 +1,10 @@
+export interface AuditLogEntry {
+  id: string;
+  ts: string;
+  actorId: string;
+  action: string;
+  target?: string;
+  status: 'ok' | 'error';
+  message?: string;
+  meta?: Record<string, unknown>;
+}