Complete Varlock runtime contract

[WalksWithASwagger]

Summary

• complete the committed environment schema against the active provider and runtime code surface
• add agent-safe validation, audit, staged scan, and non-secret child-injection smoke commands
• add repository agent instructions that prohibit reading value files or printing process environments
• preserve the existing Node and npm runtime contract by keeping the Varlock CLI externally installed

Verification

• npx --yes varlock@1.10.0 load --agent --show-all
• npx --yes varlock@1.10.0 audit
• npx --yes varlock@1.10.0 run --inject vars -- node scripts/varlock-injection-smoke.mjs
• npx --yes varlock@1.10.0 scan --staged
• npm run verify (511 passed; docs, public boundary, dry-run smoke, and package boundary passed)
• cached diff check and local-path/credential-shaped addition review

Acceptance Self-Check

• Schema coverage matches the active provider-facing code surface.
• Agent instructions prohibit reading environment value files and printing process environments.
• The non-secret smoke proves Varlock injection reaches the child process.
• Existing tests pass.
• No real value, machine path, ignored value file, or provider setting was exposed or changed.
• Diff stays within the agentic delivery size limit.

Closes #310

[github-actions]

Agentic PR Review

Verdict: review-ready

Checks:

• Linked issue via Closes #... or Refs #...: yes
• Issue acceptance criteria found: 5
• PR verification section present: yes
• PR acceptance self-check present: yes
• Diff within v1 limits: yes

[WalksWithASwagger]

Codex review: APPROVE. Added schema names map to active provider, doctor, browser, and smoke consumers; the non-secret injection sentinel is safe; 511 tests, audit, scan, secret scan, and review checks pass. No blocking findings.