Stop a mock deployment passing as a real one

[16francej]

Follow-up to #22.

HARNESS unset means mock, and mock answers every message with canned text while calling no model provider. Nothing said so. Scaffold with --model-provider openrouter, delete HARNESS from env.core, and:

• qm check passes clean
• qm doctor passes — and reported OPENROUTER_API_KEY accepted, serving openrouter/auto
• qm up deploys

The operator gets a stack that signs people in, accepts messages, and replies with nothing real behind it. Same shape as the bug #22 removed, in its quieter form: that one at least refused the first message out loud.

Two changes

Doctor stops claiming a model it never checked. The key probe is real; the model half was a guess, since doctor never looks at the harness. Now:

- base model provider openrouter: OPENROUTER_API_KEY accepted, serving openrouter/auto
+ base model provider openrouter: OPENROUTER_API_KEY accepted

MODEL_PROVIDER_BASE_MODELS existed only to render the deleted half and now has no production caller, so it goes, along with the drift test pinning it to the core registry — a table nothing reads cannot drift into anything. MODEL_PROVIDER_HARNESSES and its drift test stay; validateModelProvider reads that one.

All three gates name a mock deployment. qm check and qm doctor share one mockHarnessWarning so the wording cannot drift, and core warns at boot when NODE_ENV=production resolves to mock, next to the existing sprites warning.

qm check is the one that matters: it never reaches doctorCommon — only up, fly deploy and aws deploy do — so it was the gate every operator runs and the only one that never mentioned this.

! env.core.HARNESS is unset, which means "mock": this deployment answers every message
  with canned text and calls no model provider. Set it to "pi" for a deployment that
  runs real agent turns.

Scope

Warnings only. Mock stays reachable and unblocked: deployment.md offers it for a local test drive, and 101 of the root suite's 369 test files reach it through testConfig's default.

Two things deliberately left out:

• Refusing unset HARNESS in production. Cleaner than a warning — deploy/core/Dockerfile pins ENV NODE_ENV=production, so it is a precise signal, and only two test fixtures would need a line. It is a behaviour change and wants its own review.
• PUBLIC_API_URL silently dropping out of the required set under mock (it is gated on pi/opencode/codex). That is a secret-catalog change, not a warning, and moves what qm up demands.

Verification

Warning confirmed firing through the real CLI on the exact scenario above. CLI suite 485/485, affected core tests 53/53, tsc clean on core, CLI and contract projects; eslint, oxlint --deny-warnings, prettier --check, knip clean.