build_from_json's #1145 ghost-duplicate merge keyed on (Path(source_file).name,
label), discarding the directory, so unrelated nodes from different files sharing
a common basename (index.md, README.md, ...) and a generic label were silently
merged onto one survivor with their edges rewired — corrupting multi-corpus doc
graphs. The AST/LLM ghost twins the merge legitimately targets always share the
same source_file, so keying on the full normalized source_file preserves #1145
while making cross-directory false merges impossible. This subsumes the
#1753/#1257 cross-file ambiguity guard (now removed as dead code). Independent of
the #2032 label pass. Updated the #1257 test to the now-correct precise merge.
safishamsi
cdeba1dcb7