A path query matches every node in the file, so resolution ends in
_prefer_file_node. Two of its passes compare the label to the bare
basename, which #2032's disambiguation rewrote to a unique path suffix
(alpha/hooks.py); the third pass trusts L1 uniqueness, which a module
docstring (a rationale node on line 1) or a one-line top-level
definition also occupies.
Accept a label that names its own source_file, using the
_is_file_node_label predicate build/analyze already share. Runs before
the L1 fallback, so extra L1 nodes no longer decide the result.
(cherry picked from commit b80626ed3b)