feat(desktop): add MCP server setup and connection testing

[sentryshub]

Implements #40335

Issue for this PR

Closes #40335

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Adds an MCP settings page to the Desktop app so servers can be managed without
hand-editing the config or dropping to the CLI.

Backend (packages/opencode):

• MCP.Service.test(name, config) reuses the existing connect path (create)
  but closes the client instead of storing it, so it never mounts the server.
  It returns { status, reachable, authStatus, tools, instructions?, error? }.
  Reachability is derived from the connect result (a failed status = not
  reachable; needs_auth/needs_client_registration still count as reachable),
  auth status reuses the same token/expiry check as getAuthStatus, and tools
  come from the normal catalog discovery.
• save/remove persist to the global config via a new
  Config.updateGlobalMcp, which uses jsonc-parser modify on mcp.<name> —
  the same write path as opencode mcp add, so the CLI and Desktop stay
  consistent and comments/formatting are preserved. Both also update the running
  instance so status reflects immediately.
• New endpoints on the instance HTTP API: POST /mcp/test, PUT /mcp/:name,
  DELETE /mcp/:name.

UI (packages/app): a new MCP tab in settings that lists configured servers,
toggles enable/disable, edits/removes them, and an add/edit dialog with a Test
Connection button that shows the result inline. Servers reporting needs_auth
get an Authenticate button wired to the existing OAuth flow. The v2 SDK was
regenerated from the server to expose the new endpoints.

How did you verify your code works?

• bun run --cwd packages/opencode typecheck and bun run --cwd packages/app typecheck both pass.
• Added HTTP API tests for the new endpoints in test/server/httpapi-mcp.test.ts
  (test-without-persist, save+remove, not-found on remove); full file passes 8/8.
• Regenerated the SDK with bun run --cwd packages/sdk/js build (runs bun dev generate) and confirmed the app still typechecks against it.

Screenshots / recordings

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search, I found one potentially related PR (excluding the current PR #43719 itself):

Related PR:

• PR fix(desktop): add retry logic with exponential backoff to health check system #42422: fix(desktop): add retry logic with exponential backoff to health check system
  • fix(desktop): add retry logic with exponential backoff to health check system #42422
  • This addresses desktop MCP server health checking, which is closely related to the connection testing functionality being added in PR feat(desktop): add MCP server setup and connection testing #43719.

The other MCP-related PRs found (#40125 on trust configuration, #42429 on WSL mode, and others) appear to address different aspects of MCP functionality rather than duplicate efforts on setup and connection testing.

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[sentryshub]

The following comment was made by an LLM, it may be inaccurate:

Based on my search, I found one potentially related PR (excluding the current PR #43719 itself):

Related PR:

• PR fix(desktop): add retry logic with exponential backoff to health check system #42422: fix(desktop): add retry logic with exponential backoff to health check system

  • fix(desktop): add retry logic with exponential backoff to health check system #42422
  • This addresses desktop MCP server health checking, which is closely related to the connection testing functionality being added in PR feat(desktop): add MCP server setup and connection testing #43719.

The other MCP-related PRs found (#40125 on trust configuration, #42429 on WSL mode, and others) appear to address different aspects of MCP functionality rather than duplicate efforts on setup and connection testing.

no - these PRs are not related

[sentryshub]

@Brendonovich this is something we need for our mcp as well. our current instructions to setup our MCP for opencode vs other tools is unnecessarily complex. let me know if this PR makes sense