Refine ask retrieval and init UX

[itsflaid]

Summary

• tighten ask retrieval with intent-aware focused context, confidence thresholds, and local low-confidence answers
• ground AI answers to selected context so existing files are not invented
• clarify stale snapshot warnings and simplify devmap init with the welcome panel and Groq-only provider flow

Verification

• pnpm test:cli
• pnpm build:cli
• git diff --check

Closes #27