fix(ci): route root npm manifest changes into the Python lane

The change classifier treated package.json / package-lock.json as
python-irrelevant, so a lockfile-only PR skipped the Python lane entirely.
But several Python invariant tests read these files (assistant-ui tap cluster,
electron pin, lazy-deps, lockfile churn) — so a lockfile change can break the
Python suite. #63970 merged green (Python skipped on the PR) then reddened main
(push fails open and runs everything).

Drop root npm from the _py_irrelevant denylist so lockfile changes run Python,
honoring the classifier's own contract: never skip a lane a change could break.
Root npm still triggers the frontend lane as before.

scripts/ci/classify_changes.py

@@ -56,7 +56,11 @@ def _is_docs(p: str) -> bool:
 
 
 def _py_irrelevant(p: str) -> bool:
-    return _is_docs(p) or p in _ROOT_NPM or p.startswith(_PY_SKIP) or p.startswith(_DOCKER_META)
+    # Root npm manifests are NOT python-irrelevant: several Python invariant
+    # tests read package.json / package-lock.json (tap-cluster, electron pin,
+    # lazy-deps, lockfile churn), so a lockfile-only change can break the Python
+    # suite. Omitting them here is what let #63970 merge green then redden main.
+    return _is_docs(p) or p.startswith(_PY_SKIP) or p.startswith(_DOCKER_META)
 
 
 def _is_scan(p: str) -> bool:

tests/ci/test_classify_changes.py

@@ -50,8 +50,10 @@ CASES = {
     "uv.lock → python": (["uv.lock"], _lanes(python=True)),
     "ts package → frontend": (["apps/desktop/src/app.tsx"], _lanes(frontend=True)),
     "ui-tui → frontend": (["ui-tui/src/entry.ts"], _lanes(frontend=True)),
-    # Lockfile bump shifts every TS package's tree, but not the Python suite.
-    "root lockfile → frontend, not python": (["package-lock.json"], _lanes(frontend=True)),
+    # Lockfile bump shifts every TS package's tree AND feeds Python invariant
+    # tests that read package-lock.json (tap-cluster, electron pin, lazy-deps).
+    "root lockfile → frontend + python": (["package-lock.json"], _lanes(frontend=True, python=True)),
+    "root package.json → frontend + python": (["package.json"], _lanes(frontend=True, python=True)),
     "website → site": (["website/docs/intro.md"], _lanes(site=True)),
     # SKILL.md reads like docs, but the skill-doc tests read skills/, so a
     # skill edit must still run Python.