check:embedder-keys asserts regions-mfe forwards the documented embedder keys to its panes, and that
profile and instanceId are NOT forwarded (the host's would overwrite each pane's own and collapse both tabs
into one view). Negative-tested both ways: removing dataSource fails naming it; adding profile fails naming
the collapsed-tabs risk.
The gate lives in the plugin's scripts/ folder, as nine check: entries already do. Its comment stripper is
committed beside it (strip-code.mjs), because a committed gate cannot import from the gitignored QA folder.
Registered in scripts (alphabetical, with its //scripts note) and in gates:post; source-only, ~0.2s.
dc226c2e01