[RFE] Add automatic Codex MCP registration via config.toml

[jsfan3]

Summary

Please make MCP → Install in MCP Hosts able to register and unregister a Codename One application's MCP server in Codex automatically, instead of detecting Codex but requiring manual configuration.

Codex stores its MCP server configuration in ~/.codex/config.toml. The ChatGPT desktop app, Codex CLI, and the Codex IDE extension share that configuration on the same host, so supporting it would make the existing Codename One installation action useful across all three clients.

Current behavior

At commit ac826b1, MCPClientRegistrar knows where to find Codex's configuration on macOS, Windows, and Linux:

.codex/config.toml

However, Codex is deliberately registered as non-writable because the current implementation only knows how to update JSON hosts using an mcpServers object. Both register() and unregister() skip clients marked non-writable.

As a result, Codex can be detected and shown to the user, but Install in MCP Hosts cannot complete the registration or later remove it.

This differs from Codex's documented format, where each MCP server is represented by a TOML table such as:

[mcp_servers.example]
command = "example-command"
args = ["first-argument", "second-argument"]

[mcp_servers.example.env]
EXAMPLE_VARIABLE = "value"

The example above only illustrates the Codex format; the actual values should come from the existing MCPClientDescriptor generated by Codename One.

Official Codex documentation:

• Model Context Protocol: connect Codex to an MCP server
• Codex configuration reference

Requested behavior

When the user explicitly chooses Install in MCP Hosts, Codename One should be able to add the current descriptor to the Codex configuration using the corresponding [mcp_servers.<server-name>] table:

• map command, args, and optional environment variables from MCPClientDescriptor to valid TOML;
• create ~/.codex/config.toml and its parent directory when necessary;
• update an existing entry with the same server name without creating duplicates;
• preserve unrelated Codex settings and other MCP server entries;
• quote and escape server names, paths, arguments, and values correctly;
• refuse to rewrite a configuration that cannot be parsed safely, with a useful message instead of risking data loss;
• make the corresponding remove action delete only the Codename One server entry;
• report that Codex must be restarted or reloaded before the new server becomes available.

The implementation details are up to the maintainers; the important user-visible result is that Codex becomes a writable host in MCPClientRegistrar and that the existing install/remove workflow operates safely on a pre-existing Codex configuration.

Desired result

After selecting Install in MCP Hosts:

1. Codex is reported as successfully updated rather than as a manual-only client.
2. The Codename One MCP server appears in Codex without hand-editing config.toml.
3. Existing Codex settings remain unchanged.
4. Repeating the operation updates the same entry rather than duplicating it.
5. Removing the registration removes only that entry.

Relevant versions

• Codename One framework: 7.0.267
• Source audited on master: ac826b1df873e52f3965928c21c22f17cb1d303e
• Codex configuration format: ~/.codex/config.toml with [mcp_servers.<server-name>] tables

Why this matters

Codename One already has the host detection, the MCP descriptor, and an explicit installation action. Codex is also already present in the host registry. Supporting its configuration format would close the remaining gap and give Codex users the same one-action setup offered to writable JSON-based MCP hosts.

[shai-almog]

Done: #5724