feat(bigquery): support application default credentials

[luc443]

Summary

• require an explicit BigQuery project_id as the canonical billing project
• use Google Application Default Credentials when credentials_json is omitted
• retain explicit credential references as an override for non-ADC environments
• route live queries, scanning, local query-history ingest, and query-history probes through the same resolver
• make interactive and non-interactive setup ADC-first and update status, docs, and the public skill

Verification

• focused BigQuery connector, setup, status, local adapter, and query-history tests
• complete default @kaelio/ktx CLI test suite
• workspace type-check
• production build
• Biome and Knip dead-code checks
• live ktx connection test against BigQuery using local ADC with no credentials_json

Configuration

connections:
  warehouse:
    driver: bigquery
    project_id: my-gcp-project
    dataset_ids:
      - analytics

Cloud-hosted workloads can now use their assigned service identity without distributing a long-lived service-account key.

[vercel]

@luc443 is attempting to deploy a commit to the Kaelio Team on Vercel.

A member of the Team first needs to authorize it.