mcp: fix status() to not overwrite connected with failed

[shuv1337]

Fix MCP status showing servers as failed when connected

Summary

• Correct MCP.status() logic to avoid overwriting a connected status with failed.
• This resolves the UI showing gh_grep and chrome-devtools as failed despite being usable.

Details

• Previous logic set result[key] = "connected" when the client existed, but then immediately set result[key] = "failed" unconditionally. Added a continue to preserve connected.
• Keeps the existing response shape: Record<string, "connected" | "failed" | "disabled">, matching opencode-web's current expectations.
• Note: sst/opencode's opentui branch returns { name: { status } }. If/when we adopt that shape, we'll align the web client accordingly. For now, this PR fixes correctness without changing the API shape.

Verification

• In opencode-web, /mcp drives the McpStatus component. After this change, servers with active clients report connected and render green.

Upstream

• The opentui branch appears to have addressed this; this fork PR ensures we are unblocked now while upstream changes land.