feat(feature-flags): add wizard feature-flags command

[talagluck]

Summary

• Adds a top-level wizard feature-flags command that adds PostHog feature flag code to a project.
• Shape mirrors ai-observability: context-mill's feature-flags skill group ships one variant per language/framework with no example apps to detect against, so this program does no framework matching itself — the agent loads the skill menu (load_skill_menu with category: "feature-flags"), matches the project's manifest, and installs the right variant (see the customPrompt in src/lib/programs/feature-flags/index.ts).
• New program is registered in program-registry.ts, wired into bin.ts, and pinned in the switchboard to anthropic + Sonnet 5 (same binding shape as ai-observability).
• Companion PR on the context-mill side adds a related but separate audit skill, flag-health (wizard audit flag-health), which checks an existing flag integration for drift against PostHog's live roster — this command instead adds flags to a project that doesn't have them yet: feat(flag-health): add PostHog flag roster alignment audit skill context-mill#384

Test plan

• pnpm build — compiles clean, smoke tests and warlock smoke tests pass
• pnpm test — 2587 tests pass (161 files)
• pnpm lint — 0 errors (pre-existing warnings elsewhere in the codebase are untouched by this change; no new warnings in the added files)

🤖 Generated with Claude Code

https://claude.ai/code/session_01HBZpxnSyEjzrmLLUpgPVR3

[talagluck]

This was the wrong program (generic feature-flags installer, not flag-health). Closing in favor of a PR against my fork with the actual flag-health wiring.