fix(agents): send "improve instructions" to an agent that can act on it

[pedrofrxncx]

Follow-up to #7027.

The bug

#7027 retired the Agent Manager and moved agent CRUD into Super-Agent-only built-ins (gated on isDecopilot). The agent editor's improve instructions button dropped its manager mention along with it, so the message goes to whoever the side panel chat runs as. On /$org/agents that is the agent being edited — useRouteVirtualMcpId resolves ?virtualmcpid= (layouts/thread-route.ts:139, chat-context.tsx:377) — and that agent has no agent CRUD tools. The request had nowhere to land.

Fixed by mentioning the Super Agent, so the SUBTASK runs under a decopilot id that carries the built-ins. With both callers passing a manager again, buildImprovePromptDoc's optional-manager branch is dead code — reverted it and its tests.

Catalog connect

Connecting an MCP from the catalog no longer navigates on its own. The existing success toast gains an Open connection action, keeping the same target logic: the first tool carrying a ui:// resource, else the connection's own page (tools tab), and no button when the server lists no tools. The slug for that link now comes from the created row rather than the request payload — the server owns it.

Also

isDecopilot's comment claimed Decopilot aggregates all org connections; storage/virtual.ts findById returns none. That fact is the premise the built-ins rest on.

Testing

bun run lint (0 errors), bun test on the touched files, bun run --cwd=apps/web check. Not exercised in a browser.

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Summary by cubic

Fixes the agent editor's "improve instructions" button so it directs the request to the Super Agent, which owns the agent CRUD tools, instead of the agent being edited (which can't act on it). Also changes catalog MCP connection success to show an "Open connection" action on the toast instead of navigating automatically.

• Mentions the Super Agent in the improve instructions doc so SUBTASK runs under a decopilot id.
• Reverts the optional-manager branch in buildImprovePromptDoc since both callers now pass a manager.
• Catalog connection toast gets a button linking to the first tool carrying a ui:// resource, else the connection's own tools tab; no button when the server lists no tools.
• The link slug now comes from the created row rather than the request payload.
• Corrects the isDecopilot comment about Decopilot aggregating connections.

^{Written for commit 2bb5f39. Summary will update on new commits.}