feat(library): require questions for displayed documents

[simple-agent-manager]

Summary

• Require question on display_from_library and remove the caption/title-style display contract
• Add validated lineGroups with a 3-line default context marker for document cards
• Preserve/render question and line group metadata in project chat document cards

Verification

• pnpm --filter @simple-agent-manager/shared build
• pnpm --filter @simple-agent-manager/providers build
• pnpm --filter @simple-agent-manager/cloud-init build
• pnpm --filter @simple-agent-manager/ui build
• pnpm --filter @simple-agent-manager/acp-client build
• pnpm --filter @simple-agent-manager/terminal build
• pnpm --filter @simple-agent-manager/api test -- mcp-library-tools compact-mode
• pnpm --filter @simple-agent-manager/web test -- document-card
• pnpm --filter @simple-agent-manager/api typecheck
• pnpm --filter @simple-agent-manager/web typecheck

Notes

This branch implements the current library-document question/line-group contract. The separate SSE acknowledgement event discussed in chat should be added where the final question stream endpoint is implemented.

[codspeed-hq]

Merging this PR will not alter performance

✅ 6 untouched benchmarks

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_{Comparing sam/kv-chat-caching-stuff-7rppw3 (333f444) with main (6b76580)}

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[simple-agent-manager]

Closing this because I opened it from a branch/context misunderstanding. The intended architecture viewer work is being pushed to existing PR #1817 instead.