* fix(ci): skip portable report merge when shards are skipped
The portable consumer can still run after an upstream build failure, even though the test-shard matrix is skipped and no Vitest blob artifacts exist. Guard artifact download and both report merge variants on successful shards; retain the required-shard gate so skipped or failed shards remain failures.
This applies the report-consumer condition from ee0256c740 to current pinned main without changing action pins or required gates.
* fix(ci): preserve failed shard diagnostics
* docs: clarify current revision CI policy