fix: add purge_unknown tests and wire clean command into docs/agent config

- Add three unit tests for FindingsStore.purge_unknown: noop when
  state_dir missing, keeps allowed names, removes unknown files and dirs
- Document pythinker-review clean command in README alongside clean-locks
- Add pythinker review clean guidance to code_reviewer.yaml so the agent
  knows to use it for stale review state maintenance

Author: elkaix

packages/pythinker-review/README.md

@@ -105,8 +105,8 @@ Phase 1 now ports the highest-value behavior from the mounted blackbox repos:
   outside the reviewed chunk/feature, unsafe paths, omitted/truncated line ranges, or non-matching
   evidence snippets; invalid sibling findings are recorded as drops without failing the whole run.
 - Reviewflow pure-Python stateful commands cover `init`, `map`, `status`, `review`, `ci`,
-  `report`, `show --finding`, `next`, `triage`, `revalidate`, `fix`, `open-pr`, `doctor`, and
-  `clean-locks`.
+  `report`, `show --finding`, `next`, `triage`, `revalidate`, `fix`, `open-pr`, `doctor`,
+  `clean-locks`, and `clean` (removes unexpected entries from `.pythinker-review/`).
 - Code-review prompt parity covers partial-diff caveats, concrete trigger scenarios, test analysis,
   suggested regression tests, and minimum fix scope.
 - Code-reviewr PR assistant parity adds read-only `describe`, `improve`/`suggest`, `ask`,

packages/pythinker-review/tests/unit/test_findings_store.py

@@ -78,3 +78,36 @@ def test_begin_twice_without_finalize_raises(tmp_path: Path) -> None:
     with pytest.raises(RuntimeError, match="begin\\(\\) called twice"):
         store.begin(meta)
     store.finalize(meta)
+
+
+def test_purge_unknown_noop_when_state_dir_missing(tmp_path: Path) -> None:
+    store = FindingsStore(repo_root=tmp_path)
+    assert store.purge_unknown() == []
+
+
+def test_purge_unknown_keeps_allowed_names(tmp_path: Path) -> None:
+    state_dir = tmp_path / ".pythinker-review"
+    state_dir.mkdir()
+    (state_dir / "index.json").write_text("{}", encoding="utf-8")
+    (state_dir / "runs").mkdir()
+    (state_dir / "security-scan").mkdir()
+    store = FindingsStore(repo_root=tmp_path)
+    assert store.purge_unknown() == []
+    assert (state_dir / "index.json").exists()
+    assert (state_dir / "runs").exists()
+    assert (state_dir / "security-scan").exists()
+
+
+def test_purge_unknown_removes_unknown_file_and_dir(tmp_path: Path) -> None:
+    state_dir = tmp_path / ".pythinker-review"
+    state_dir.mkdir()
+    stray_file = state_dir / "stray.json"
+    stray_file.write_text("{}", encoding="utf-8")
+    stray_dir = state_dir / "old-report"
+    stray_dir.mkdir()
+    (stray_dir / "data.txt").write_text("x", encoding="utf-8")
+    store = FindingsStore(repo_root=tmp_path)
+    removed = store.purge_unknown()
+    assert set(removed) == {"stray.json", "old-report"}
+    assert not stray_file.exists()
+    assert not stray_dir.exists()

src/pythinker_code/agents/default/code_reviewer.yaml

@@ -10,6 +10,7 @@ agent:
       - Use `pythinker review diff` by default for bounded branch/diff review; add `--with-security` when the parent requests security coverage.
       - For repo-wide, long-running, resumable, or feature-slice review requests, prefer the stateful flow: `pythinker review init`, `pythinker review map`, then `pythinker review review --limit <n> --jobs <n>` followed by `report`/`next`/`show`/`triage` as needed.
       - Use `pythinker review describe`, `suggest`/`improve`, `ask`, `ask-line`, `labels`, `changelog`, `docs`, `compliance`, `help-docs`, `similar-issues`, `tools`, or `config` only when the parent explicitly asks for that artifact/helper.
+      - Use `pythinker review clean` to remove unexpected entries from `.pythinker-review/` when the parent requests maintenance or cleanup of stale review state; pass `--dry-run` first to preview what will be removed.
       - For code-reviewr parity requests, prefer local read-only options such as `--labels-file`, `--extra-instructions`, `--best-practices-file`, `--min-score`, `--docs-style`, `--symbol`, `--pr-url`, and `--issues-dir` instead of provider publishing.
       - Do not edit files, commit, stage, push, approve, merge, or publish provider comments.