Add Codex agent configuration support

[rayenchtioui]

Summary

Adds Codex as a first-class DebugMCP agent configuration target.

DebugMCP already exposes a Streamable HTTP MCP endpoint at /mcp; this change lets the extension configure Codex automatically by writing the matching MCP server entry to Codex's config.toml.

Changes

• Adds Codex to the agent setup flow
• Writes DebugMCP configuration to ~/.codex/config.toml, or ${CODEX_HOME}/config.toml when CODEX_HOME is set
• Preserves existing Codex TOML content while upserting [mcp_servers.debugmcp]
• Migrates an existing DebugMCP /sse Codex URL to /mcp
• Documents Codex setup in the README and architecture notes
• Adds focused tests for Codex TOML upsert behavior

Validation

• npm run compile
• npm run lint
• npm test - 13 passing
• Manually verified the extension setup flow writes the Codex MCP config and Codex recognizes debugmcp as a streamable_http MCP server

[rayenchtioui]

@microsoft-github-policy-service agree