feat(cli): accept both bare flags and legacy yes/no for --if-add-* args

Resolves PR #272 review #10/P5. The --if-add-node-id / -node-summary /
-doc-description / -node-text args were store_true, which rejected the
documented yes/no values and left default-on options impossible to disable
from the CLI. They now use nargs='?' + const=True + a yes/no-coercing type:

  --if-add-node-id        -> on
  --if-add-node-id no     -> off   (legacy form still works)
  (omitted)               -> use the IndexConfig default

README updated to the flag usage (noting the legacy `no` off-switch), and
--if-add-node-text is now documented too.

Decisions from the review:
- #7 (api_key semantics): verified FALSE POSITIVE — 0.2.x is a cloud SDK whose
  api_key is a PageIndex cloud key (cloud_api.LegacyCloudAPI + docs.pageindex.ai/sdk),
  matching the new SDK. No change.
- #11 (if_add_doc_description default True): kept intentionally (open mode).

Claude-Session: https://claude.ai/code/session_01Kx5DgKbhK1N8autqXH8SmS

tests/test_review_fixes.py

@@ -128,3 +128,13 @@ def test_cloud_query_empty_collection_raises(monkeypatch):
     monkeypatch.setattr(backend, "_get_all_doc_ids", lambda col: [])
     with pytest.raises(ValueError, match="no documents"):
         backend.query("empty", "q")  # doc_ids=None -> resolves to []
+
+
+# ── #10: CLI bool flags still parse legacy yes/no (a bare 'no' must be False) ──
+def test_cli_bool_coerces_legacy_yes_no():
+    import run_pageindex
+
+    assert run_pageindex._cli_bool("no") is False   # legacy off-switch
+    assert run_pageindex._cli_bool("yes") is True
+    assert run_pageindex._cli_bool("false") is False
+    assert run_pageindex._cli_bool(True) is True     # bare flag -> const=True