Add a gated end-to-end LLM smoke test + deploy healthcheck

[dkirby-ms]

Summary

Every existing test uses mock transports or is gated behind unset flags (OPENAI_LLM_TEST), so no real LLM is ever exercised in CI, and there is no deploy-time check that narration works. Add an opt-in e2e smoke test against a real endpoint and a deploy healthcheck.

Scope / Tasks

• Add an opt-in e2e test (gated by an env flag) that calls the real provisioned endpoint via the chosen transport and asserts a valid, contract-passing completion (reuse validateLLMOutput).
• Add a post-deploy healthcheck (script or container readiness probe) that issues one narration request and verifies an LLM (not fallback) response, surfacing fallback as a warning.
• Fix/rename the misleading azure-llm-transport.integration.test.ts to reflect what it actually tests (or repoint it at the real Azure transport from Issue 3).
• Document how to run the gated smoke test locally and in CI.

Acceptance Criteria

• A gated e2e test passes against the live endpoint when the flag is set; skipped cleanly otherwise.
• Deploy pipeline reports LLM reachability (pass/fallback) for the environment.
• The vestigial test name no longer misrepresents Azure coverage.

Dependencies

#510 (config flows), #511 (transport), #514 (a real player-visible path to exercise).

Size

M

Derived from the LLM narration gap analysis (Volo) and decomposition (Elminster).