Codex MCP setup doesn't match new standard.

[Kadajett]

Summary

semfora-engine setup --clients openai-codex still assumes Codex MCP config lives in JSON files like ~/.codex/mcp.json, but current Codex stores MCP servers in config.toml (~/.codex/config.toml globally or .codex/config.toml per project) under
[mcp_servers.<name>].

Current behavior

The OpenAI Codex installer code still uses legacy JSON paths:

• ~/.codex/mcp.json
• ~/.openai/codex/mcp.json
• ~/.config/codex/mcp.json
• project .codex/mcp.json

Relevant code:

• src/installer/clients/openai_codex.rs:27-35
• src/installer/clients/openai_codex.rs:74-79
• src/installer/clients/openai_codex.rs:99-104

It also writes mcpServers JSON instead of TOML [mcp_servers.<name>].

Expected behavior

For Codex, Semfora should write either:

• global: ~/.codex/config.toml
• project: .codex/config.toml

using the current schema, for example:

[mcp_servers.semfora-engine]
command = "/absolute/path/to/semfora-engine"
args = ["serve", "--repo", "/absolute/path/to/repo"]
startup_timeout_sec = 20
tool_timeout_sec = 120

## Repro

1. Build/install Semfora.
2. Run semfora-engine setup --clients openai-codex.
3. Observe that it targets legacy mcp.json paths instead of Codex config.toml.

## Workaround

Manual project-scoped Codex config works today:

[mcp_servers.semfora-engine]
command = "/Users/jeremy.stover/.cargo/bin/semfora-engine"
args = ["serve", "--repo", "/Users/jeremy.stover/dev/semfora-engine"]
startup_timeout_sec = 20
tool_timeout_sec = 120

## Suggested fix

- Replace the Codex client implementation to read/write TOML config.
- Target ~/.codex/config.toml and .codex/config.toml.
- Model Codex separately from Claude/Cursor JSON mcpServers handling.
- Add tests covering both global and project-scoped Codex config.