feat(chat): add notebook agent harness artifacts

[EricNGOntos]

Summary

• Add the Notebook Agent Harness runtime with explicit intent declaration, context policy, retrieval ledger, manifest finalization, and validator feedback.
• Route Notebook chat through the harness so KNOWHERE remains an evidence provider while the outer agent handles intent, planning, retrieval, artifact selection, and answer shaping.
• Persist chat artifacts and render selected image artifacts before legacy image citation fallback, so requests like 'only 2 images' show the agent-selected set.
• Add the chat message artifacts migration and clear local release checks, including the Next SWC lockfile patch.

Validation

• pnpm run typecheck
• pnpm test
• pnpm run lint (passes with one existing warning in src/domains/sources/route-upload.ts)
• pnpm run build
• Real local trajectory checks with DeepSeek + local Knowhere: unrelated follow-up isolated with carryHistory=none; image-count request produced desiredCount=2/maxCount=2 and displayedArtifactCount=2.

Effect Guides Consulted

• effect-solutions: basics
• effect-solutions: data-modeling

Release notes

• Requires production env to have AI_GATEWAY_API_KEY, DATABASE_URL, KNOWHERE_BASE_URL, NOTEBOOK_PUBLIC_URL, and QSTASH_TOKEN where background reconcile is expected.
• Requires DB migration 0008_chat_message_artifacts.sql before relying on persisted artifacts.
• No KNOWHERE-MAIN navigation changes are included; KNOWHERE remains the retrieval/evidence provider.

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Project	Deployment	Actions	Updated (UTC)
knowhere-notebook-staging	Ready	Preview, Comment	Jun 12, 2026 1:47pm

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
knowhere-notebook	Ignored		Jun 12, 2026 1:47pm