Name the existing Trino API cell legacy

[benben]

Summary

• Name the existing single-deployment Trino API identity legacy.
• Keep persisted ownership IDs, catalog-store keys, provisioner configuration, and connection endpoints unchanged.
• Match connection readiness against persisted ownership, including when a foreign stored ID happens to equal the API alias.

This is a naming/compatibility change only. It adds no cell registry, selection endpoint, tenant migration, or database migration. The general org endpoint continues to expose the original trino.trino_cell_id; unassigned and foreign-cell rows keep their existing values.

Validation

• TDD: new alias/identity tests failed before implementation, then passed.
• just test-controlplane-k8s with a disposable local PostgreSQL fixture.
• just lint (0 issues).
• just ui-test (26 files, 186 tests, typecheck and production build).
• sh -n tests/mw-dev/e2e/trino.sh and git diff --check.
• The existing isolated Trino end-to-end assertions now check both legacy API labels and unchanged persisted ownership. Their live execution is left to normal PR CI; no existing tenant or deployed configuration was changed manually.

Compatibility and recovery

API consumers displaying the previous cell ID now receive legacy for the existing deployment. Do not change stored IDs or DUCKGRES_TRINO_CELL_ID to match this display name. Roll back the application version if a consumer requires the previous displayed ID.

[github-actions]

Test Impact Plan

Deterministic summary of how this PR changes tests, CI runners, and coverage-risk signals.

Summary

Area	Added	Changed	Deleted
Test files	1	2	0
E2E/journey files	0	0	0
Workflow files	0	0	0

Signals

• Test cases: +2 / -0
• Assertions: +9 / -0
• Skips or known failures added: 0
• Workflow continue-on-error added: 0
• Workflow path filters added: 0
• Test commands removed from justfile: 0
• E2E/journey retry lines added: 0

Coverage risk: neutral or increased

No coverage-reduction warnings detected.

[bill-ph]

Reviewed the current head and Trino API identity changes. The alias is confined to public API views while persisted ownership IDs and connection readiness continue to use the stored ID; focused regression coverage and all completed required checks pass. No P0 blockers requiring code changes found. Remaining end-to-end lanes are still pending.

— Robo Bill