docs: complete tested Doris and ClickHouse authoring walkthrough

[meaningforger]

Summary

Complete the Doris/ClickHouse table-to-query authoring walkthrough in one PR.

• Add disposable setup SQL, reference-only connection configuration, exact selectors/maps, and runnable capture/generation scripts.
• Keep generated technical row counts separate from an explicitly reviewed, manually authored revenue definition; business-model adoption remains a visible manual step.
• Add independently reviewed integer/decimal expectations, runtime suite commands, and authenticated local REST querying.
• Exercise the actual CLI, checked-in scripts, server startup, authentication and result semantics in the existing real-engine tests. The Doris tutorial uses a separately provisioned authenticated reader.
• Cover model/suite/request consistency, both compile dialects, existing-directory refusal, unsafe endpoint rejection and authenticated request-script behavior in default tests.
• Correct stale generated guidance and synchronize README, authoring/extension contracts and RFC-0089's implemented Doris/ClickHouse status. Optional DuckDB catalog support remains deferred; no new runtime API or fixture-provisioning feature is introduced.

Validation

• make check
• make docs-check, make fmt-check, git diff --check
• GORACE=atexit_sleep_ms=0 go test -race ./cmd/metis ./app/tooling/authoring
• Doris and ClickHouse full real-engine matrix: both passed, including TestAuthoringWalkthroughThroughCLIAndREST.
• Standard PR CI: all checks passed.

The human 30-minute walkthrough remains an unmeasured usability target. The capture/request shell helpers never create database objects, grant privileges, approve a business definition, or delete existing data. Setup SQL is deliberately executed separately with the database client in a fresh disposable warehouse.