Verify first-agent docs commands in CI

[asim]

Goal: keep the developer-adoption on-ramp honest by turning the README/website first-agent path into a small CI-verifiable command contract, so scaffold -> run -> chat -> inspect docs cannot drift from runnable behavior.

Scope:

• Add or extend a focused no-secret harness that exercises the documented first-agent command sequence and examples wayfinding.
• Prefer existing mock-model fixtures and short-running checks; do not require live provider keys.
• Keep this to documentation-command fidelity and CLI breadcrumbs, not a public API redesign.

Acceptance criteria:

• A documented make target or Go test verifies the first-agent docs commands/breadcrumbs used by README and website guides.
• The check fails on stale command names, missing example paths, or broken no-secret first-agent entrypoints.
• README/website references point to the verified command path.
• go build ./..., go test ./..., and golangci-lint run ./... remain green.