Simplify program guidance for v0.16.4

[abewheel]

Summary

• Make control implementation guidance specific, short, and tied to the current readiness checks.
• Bring the five program stages, major page instructions, agent guides, browser, and CLI to the same guidance source.
• Release coordinated filegrc and create-filegrc version 0.16.4.

Validation

• CI=true npm run validate on Node 24
• Both npm pack --dry-run --workspace checks
• npm audit with zero vulnerabilities
• Fresh generated consumer using the local 0.16.4 engine, 228 records and no validation errors or warnings
• Three independent security and code review passes with no actionable findings