Agents page: group by workspace, add a list view, rework the org chart

[danielehrhardt]

• Grid and new List view sort agents under collapsible workspace sections in All workspaces, with working / needs-you counts and a shortcut to the workspace
• Org chart: the built-in agent as the hub on top, a panel per workspace (or per team inside one) in balanced columns, compact rows with tree connectors
• Compact agent card footer; the action menu is shared by card and row
• Search and filters open folded groups so no hit hides

What does this change?

How was it tested?

Checklist

• pnpm typecheck and pnpm test pass
• cargo clippy / cargo test pass (if apps/desktop/src-tauri changed)
• API changes are reflected in packages/shared and apps/desktop/src/lib/api.ts
• No secrets, tokens or personal data in code, fixtures, logs or screenshots
• Docs updated where behaviour changed