* refactor(context): export and describe mapping shape schemas
* feat(context): add driver-schemas module with warehouse drivers
* feat(context): add metabase, looker, lookml driver schemas with mappings
* feat(context): add notion, dbt, metricflow driver schemas
* refactor(context): make connectionSchema a driver-discriminated union
* chore(context): re-export KtxConnectionConfig from project package
* docs(context): add connection driver schema plan
* chore(secrets): allowlist example credentials in driver-schemas fixtures
* test(cli): align metabase fixtures with required api_url field
The driver-discriminated union added in this branch now requires api_url
for metabase connections and a known driver for warehouses. Update slow
CLI test fixtures and assertions so they exercise the new schema:
- ingest.test-utils.ts: add api_url to the prod-metabase fixture.
- setup.test.ts: switch metabase fixture from 'url' to 'api_url'.
- local-scan-connectors.test.ts: invalid-driver/missing-driver tests now
expect the schema error from loadKtxProject (parse-time rejection).
