feat(improvement): add resumable knowledge base loop

[drewstone]

Summary

• add improveKnowledgeBase() as the durable candidate-KB wrapper around the existing RAG lifecycle
• add run state, lock leases, candidate workspaces, resume, drift-safe promotion, KB quality scoring, answer-quality blocking, and retrieval tuning on candidate indexes
• update Tangle deps to @tangle-network/agent-eval@^0.107.0, @tangle-network/agent-runtime@^0.89.0, and @tangle-network/sandbox@^0.9.7

Verification

• pnpm exec tsc --noEmit
• pnpm exec vitest run tests/kb-improvement.test.ts tests/rag-improvement-loop.test.ts tests/rag-eval.test.ts tests/retrieval-eval.test.ts (26 passed)
• pnpm exec vitest run (259 passed, 12 skipped)
• pnpm exec tsup
• pnpm exec biome check src tests
• git diff --check
• git merge-tree --write-tree origin/main HEAD

[tangletools]

✅ Auto-approved drewstone PR — 5b562cf2

This PR was opened by the trusted drewstone account.
The full PR reviewer audit still runs separately and will publish findings if it detects issues.

_{tangletools · auto-approval · reason: drewstone_author · 2026-07-08T00:33:58Z}