The distribution test only exercised a FILE shipped over a store's
ancestor; nothing failed if _merges_per_root stopped merging a store's
ancestor DIRECTORY, which would replace platforms/whatsapp whole and
delete the installer's platforms/whatsapp/session. Ship
platforms/whatsapp/config.json over an installer-added session store and
assert the store survives (red with the
profile_path_contains_private_store clause removed).
Also name mcp-tokens, vault, platforms/pairing, slack_tokens.json and
webhook_subscriptions.json in _EXTRA_STORES so dropping any of them from
PROFILE_CREDENTIAL_PATHS fails a test, and replace the inline npmrc
special case with a _DOTLESS_FILES set.
b1ce87029d