feat(virtual-mcp): attach files and skills to agents as knowledge

[rafavalls]

What is this contribution about?

Adds a Files and skills section to agent settings so users can attach reference material an agent always has access to. Files upload to the org filesystem (the Library's home volume under knowledge/, persistent and mounted into every agent sandbox), and users can also pick existing recent Library files or any Claude Code skill folder (reusing the existing hasSkill detection). Selections are stored on metadata.knowledge and surfaced to the agent in a <knowledge> system-prompt block that lists each item's exact sandbox path and inlines small text documents. The settings sections were also reordered to Connections → Instructions → Files and skills → Sub-agents, and the Sub-agents description moved under its title.

Screenshots/Demonstration

Agent settings now show a "Files and skills" section with an "Add" dropdown (Upload file / Select file or folder / Select skill), file-type icons, and drag-and-drop.

How to Test

1. Run bun run dev, open an agent's settings, and in Files and skills upload a .md file (or drag-drop).
2. Confirm it appears in the Library under home/knowledge/, and that "Select file or folder" / "Select skill" list recent Library files and org skills.
3. Start a fresh chat with that agent and ask what files it has — it should list the file with its sandbox path and the inlined contents.

Migration Notes

No database migrations. metadata.knowledge is a new optional field on the existing virtual-MCP metadata (loose schema).

Review Checklist

• PR title is clear and descriptive
• Changes are tested and working
• Documentation is updated (if needed)
• No breaking changes

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Summary by cubic

Adds a “Files and skills” section to agent settings so you can attach Library files/folders and Claude Code skills. Attached items are stored in the org Library and surfaced to the model via a <knowledge> block appended to served instructions with exact sandbox paths.

• New Features

  • Upload or pick recent Library files/folders and skills; drag-and-drop supported. Uploads land in home/knowledge/.
  • Selections are saved on metadata.knowledge using KnowledgeFile (exported in packages/mesh-sdk); skills are detected via hasSkill across home and public sets.
  • Served instructions include a <knowledge> block that lists each item with its sandbox path (via orgFsSandboxPath); the agent reads files directly (no content inlining).
  • Settings order updated: Connections → Instructions → Files and skills → Sub-agents; Sub-agents help text moved under the title.
  • Limits: max upload 25 MB. No database migrations.

• Bug Fixes

  • Knowledge now ships in served instructions for all run paths (cluster and sandbox-daemon), replacing the previous cluster-only prompt addition.

^{Written for commit 6823561. Summary will update on new commits.}