feat: add source freshness readiness audit

[drewstone]

Summary

• bump package to 1.1.1
• add source validUntil/lastVerifiedAt fields
• make eval bundle readiness penalize expired sources
• expose source freshness counts and per-source status in inspectKnowledgeIndex
• add regression coverage for expired source blocking

Why

Domain KBs need measurable freshness before launch. This makes stale corpus coverage visible and readiness-blocking without requiring every product to hand-roll source audits.

Validation

• pnpm typecheck
• pnpm test
• pnpm build
• git diff --check