Guard first-agent wayfinding targets

[asim]

Adds a focused no-secret docs harness assertion for the first-agent adoption path.

Summary:

• Resolve first-agent wayfinding Markdown links from README, repository examples, website examples, and getting-started docs to local repo targets.
• Verify documented lifecycle command order across the 0→hero guide, CLI docs output source, and scaffold next steps.

Testing:

• go test ./internal/harness/zero-to-hero-ci -run 'TestFirstAgentWayfinding|TestFirstAgentLifecycleCommandOrderIsDocumented' -count=1\n- go build ./...\n- go test ./... (environment warning: loopback-target grpc tests are blocked by sandbox envoy)\n- golangci-lint run ./...\n\nCloses Make first-agent docs wayfinding link targets self-verifying #4064\nCloses Loop: build increment #86 #4068