MCP prompts/list failure wipes the cached prompt list and announces it as empty

The bug is in packages/core/src/mcp/index.ts around lines 305-312, where refreshPrompts handles a failed prompts/list call. Compare with refreshTools above it. The failing test is in packages/core/test/mcp.test.ts using the resourceServer fixture. Run the test to see the failure, then modify the Effect.orElseSucceed logic to preserve the existing prompts on error, similar to refreshTools.

Description

refreshPrompts turns a failed prompts/list into an empty list and then commits it: Effect.orElseSucceed(() => []) at packages/core/src/mcp/index.ts:307, and the Effect.map below it assigns entry.prompts from that empty result before publishing PromptsChanged (:305-312). refreshTools directly above (:298-303) has no such swallow, so a failed tools refresh leaves the registered tools alone. The two listings behave differently on the same failure.

So one transient error on a server that is still connected wipes its prompts, and the event that follows tells every reader the list is now legitimately empty — packages/core/src/plugin/command.ts:18-24 reacts to PromptsChanged by re-reading mcp.prompts() and calling ctx.command.reload(). The server's slash commands disappear and nothing indicates why: servers() still reports status: "connected".

Plugins

None.

OpenCode version

v2 at 681ea07a9.

Steps to reproduce

Using the resourceServer fixture in packages/core/test/mcp.test.ts, with prompts capability advertising listChanged and a responder that answers prompts/list with a JSON-RPC error once armed:

1. Connect; the initial listing succeeds and service.prompts() contains greet.
2. The server sends prompts/list_changed; the client re-lists and the server answers with the error.
3. service.prompts() is now [], while service.servers() still reports { status: "connected" }.

Expected: the failed refresh keeps the prompts it already had, as refreshTools does. The regression test in the PR fails on 681ea07a9 with prompts were [] and passes with the one-line change.