The dev:mock script duplicated the e2e mock server. The copy had only
the plain chat reply; every scripted path lived only in the e2e version.
A single mock server now lives in tests-js/scripts/mock-server.ts.
The e2e suite imports it as a library. Running the file directly
starts the server, writes a mock config, and launches the desktop app.
The dev:mock script now runs that file.
The e2e tsconfig lists tests-js/scripts in its include, because the
composite project rule requires every imported file to be listed.
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