Add CI check for Polkadot-API metadata freshness
This PR adds a new CI workflow that ensures the Polkadot-API metadata
file (`test/.papi/metadata/datahaven.scale`)
is kept up-to-date when runtime changes are made.
Changes:
- Added task-check-metadata.yml workflow that:
- Reuses the WASM artifact from the build-operator job (no duplicate
compilation)
- Runs `bun x papi add` to regenerate metadata
- Fails if the metadata file has uncommitted changes
- Integrated the check into `CI.yml` as a second-tier job alongside
`docker-build`
Why:
- Prevents TypeScript type definitions from becoming out of sync with
the runtime
- Reminds developers to run `bun generate:types:fast` when making
runtime changes
- Ensures consistent type safety across the codebase
The check provides clear error messages with instructions when metadata
is outdated.
