Split active overlay readability from file replacement tombstones. Replacement overlay publishes still hide canonical file rows, while the new additive publish API layers safe overlay facts without tombstoning the file.
Update the active-overlay CTE, node-view summary, and benchmark mirror so additive overlay rows are visible while canonical rows for the same file remain visible.
Add a store canary proving an additive overlay symbol is readable without creating a file tombstone or hiding existing canonical rows.
Validation: uv py_compile benchmark harness passed; ASan/UBSan test-runner build passed; store_nodes suite passed 108; source-safety passed; diff check clean; production build passed.
Signed-off-by: Andrew Hundt <ATHundt@gmail.com>
Andrew Hundt
170aa7d830