Stabilize provider API-key capture test

[dennisonbertram]

Closes #1052

Related: #1000, #1047, #1051, #1062

Summary

• synchronize the API-key capture test on direct provider-factory invocation instead of full HTTP readiness
• preserve the exact captured-key assertion, interrupt delivery, and bounded graceful-shutdown proof
• supersede the later 10-second HTTP readiness mitigation from [Bug]: Provider API key matrix health wait expires under race contention #1062 with synchronization on the contract this test actually owns
• keep the change test/docs-only; production startup, provider, health, and shutdown semantics are unchanged

Why

TestMatrix_ProviderAPIKeyCapture verifies that OPENAI_API_KEY reaches the injected provider factory. Waiting for the entire HTTP server to become healthy made that unit contract depend on scheduler, watcher, persistence, listener, and HTTP startup timing. The injected factory now signals after it stores the captured key, so the assertion waits on the behavior under test.

This is an independently evidenced baseline repair. It is being promoted before retrying the cron/callback merge chain; it is not being claimed as the proven cause of a later production-gate failure whose exact test output was lost.

Verification on rebased head

Exact head: 3384616a8598a7fb73638220601a4a7d24c9eced

Rebased onto: 7a1d257ce79fb71866b2ef7beff1d7ea3387e64e

• expected-red direct signal timeout before the provider factory emitted the signal
• go test ./cmd/harnessd -run '^TestMatrix_ProviderAPIKeyCapture$' -count=100 — PASS
• go test -race ./cmd/harnessd -run '^TestMatrix_ProviderAPIKeyCapture$' -count=100 — PASS
• ./scripts/test-regression.sh — PASS
  • normal suite — PASS
  • race suite — PASS
  • coverage gate — PASS (85.6%, zero-functions=0)
• git diff --check origin/main...HEAD — PASS

The old hosted race failure on the stale head was unrelated (TestExecuteLifecycle_WaitForUserFlowEventOrderAndStateRestoration). Hosted checks will rerun on this exact rebased head.

Rollout and rollback

This changes test synchronization only. Rollback is a normal revert; no runtime data, schema, or deployment migration is involved.

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[dennisonbertram]

Exact tested head: ec1109d. @codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Swish!

Reviewed commit: ec1109dc19

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