cli: mcp list / mcp auth ignore the global config — servers added with --global are invisible #55811

Summary

opencode mcp add <name> --global --url ... writes the server to
~/.config/opencode/opencode.json, but opencode mcp list and
opencode mcp auth <name> never see it — they only read project-level config.
Adding the exact same server to a project's opencode.json makes both commands
work immediately (after a service restart). opencode service restart does not
fix the global case.

Environment

• opencode version: 2.0.24
• OS: Linux 6.18.54.1-microsoft-standard-WSL2 (x64)
• Terminal: xterm-256color (WSL2)
• Shell: /bin/bash
• Install/channel: latest
• Active plugins: none configured

Reproduction

1. opencode mcp add myserver --global --url https://mcp.example.com/mcp
   → output: MCP server "myserver" added to ~/.config/opencode/opencode.json
   → file contains "mcp": { "servers": { "myserver": { "type": "remote", "url": "..." } } }
2. opencode mcp list (run from $HOME or any project) → No MCP servers configured
3. opencode service restart && opencode mcp list → still No MCP servers configured
4. Rewrite the global entry in the documented shape
   ("mcp": { "myserver": { ... } }, server name directly under mcp) →
   opencode service restart && opencode mcp list → still No MCP servers configured
5. Create a project opencode.json with the same server entry (either shape) →
   opencode service restart && opencode mcp list → ⚠ myserver needs authentication
   and opencode mcp auth myserver resolves it correctly.

Expected Behavior

Per the docs, --global makes the server "available in every project";
mcp list and mcp auth <name> should resolve servers from the global config.

Actual Behavior

• mcp list → No MCP servers configured
• mcp auth <name> → MCP server not found: <name>
• consistently reproducible across multiple service restarts, with both config shapes.

Additional Context

• mcp add --global writes the mcp.servers.<name> shape while
  https://opencode.ai/docs/mcp-servers/ documents <name> directly under mcp
  — the writer and docs disagree; both shapes behave identically in mcp list
  (i.e. ignored) when present in the global file.
• Workaround: add the server to a project-level opencode.json instead of
  --global, then restart the background service.
• Discovered while setting up an OAuth-protected remote MCP server (the CLI
  stopped at "MCP server not found" until the project-level config was used).