Add codex cli support

[albanx]

The codex CLI requires the /responses endpoint. Based on the documentation, adding by imitation codex support. Verified and worked.

Docs:

https://developers.openai.com/codex/config-advanced
openai/codex#7782
openai/codex#4278

Sample config of codex in C:\Users\username\.codex\config.toml

model = "gpt-5.3-codex"
model_reasoning_effort = "medium"
model_provider = "copilot"

[notice.model_migrations]
"gpt-5.2-codex" = "gpt-5.3-codex"

[windows]
sandbox = "unelevated"

[model_providers.copilot]
name = "copilot"
base_url = "http://localhost:4141/v1"
wire_api = "responses"

Steps to use it:

1. Configure codex config as above
2. Launch as usual npx copilot-api@latest start
3. Launch codex and start using it (if prompted go to custom API usage)

[caozhiyuan]

@albanx This PR is a duplicate; please use https://github.com/caozhiyuan/copilot-api/tree/all . The current branch supports 5.3 CodeX in Claude Code, Open Code, and CodeX.

[caozhiyuan]

apply_patch should like this https://github.com/caozhiyuan/copilot-api/blob/all/src/routes/responses/handler.ts#L108