fix(python): keep package directories off the sys.path root walk

[Yi-111-a]

Summary

resolvePythonImport() walks up from the importer's directory and tries each ancestor as a candidate sys.path root, first match wins. The walk treated every ancestor as a root candidate, including directories that contain an __init__.py.

A directory with an __init__.py is a package, and Python puts a package's parent on sys.path — never the package itself. Offering one as a root produces two wrong edges:

1. A package module shadows a stdlib / third-party name. With
   service/app/__init__.py and service/app/logging.py, the bare import logging inside service/app/logging.py resolved to the in-tree file, so every sibling importing the real stdlib logging picked up a false in-tree edge.
2. A module resolves to itself. That same service/app/logging.py got the edge service/app/logging.py → service/app/logging.py. Separately, import svc.main from src/svc/main.py reached itself whenever an enclosing namespace directory was a root candidate.

Closes #621.

Changes

In understand-anything-plugin/skills/understand/extract-import-map.mjs, the absolute-import branch of resolvePythonImport():

• skips a candidate root that carries an __init__.py;
• drops a match equal to the importing file, so the walk continues to a shallower root rather than returning early.

The two rules are independent: the first covers a package under a real root, the second covers the PEP 420 namespace-package case where there is no __init__.py to key on.

The multi-service case is preserved

This is the case the walk-up exists for, and both rules leave it alone: src/emailservice/ carries no __init__.py, so it stays a valid implicit root and import demo_pb2_grpc still resolves to src/emailservice/demo_pb2_grpc.py. The existing regression test for it is unchanged and still passes. A skipped package's parent is still a candidate on the next iteration, so the genuine from app.logging import get_logger edge survives.

Verification

Two new regression tests in tests/skill/understand/test_extract_import_map.test.mjs, both of which fail on main and pass with this change:

• does not treat a package directory as a sys.path root — asserts service/app/logging.py gets no edges for its bare import logging, and that service/app/main.py still resolves to service/app/logging.py.
• never resolves a python import to the importing file — asserts import svc.main from src/svc/main.py is not a self-edge while the real import helpers sibling edge is kept.

Before the fix, the first test observed the self-edge directly:

AssertionError: expected [ 'service/app/logging.py' ] to be undefined
AssertionError: expected [ 'src/svc/helpers.py', …(1) ] to deeply equal [ 'src/svc/helpers.py' ]
+   "src/svc/main.py",

After:

pnpm install
pnpm --filter @understand-anything/core build
pnpm vitest run tests/skill/understand/test_extract_import_map.test.mjs --testTimeout=60000
# Test Files  1 passed (1)
#      Tests  69 passed (69)

pnpm eslint understand-anything-plugin/skills/understand/extract-import-map.mjs \
  tests/skill/understand/test_extract_import_map.test.mjs   # clean

All 69 tests in the file pass, including the 67 pre-existing ones. --testTimeout is only needed on a loaded machine: the suite spawns a node subprocess per case, and the default 5 s per-test timeout can trip on an unrelated case.

Notes

• No CLA or AI-contribution restriction applies to this repository.
• Scope is the resolver only. The issue also mentions broader stdlib-shadowing cases (types.py, json.py, email.py, queue.py) — those are the same defect and are covered by the same rule, since the skip keys on __init__.py rather than on any module name.