feat: Codex v0.114.0 integration with gpt-5.4 support

[CaddyGlow]

Summary

• Refactored Codex adapter request preparation with separate header/body handling and content-encoding passthrough
• Added request template application from detection cache and input message normalization
• Added WebSocket handler foundation for realtime API with async model listing
• Narrowed fallback exception types in detection service for safer error handling

PR Stack

This is PR 1 of 3 split from #41. Merge in order:

1. This PR - Core Codex v0.114.0 integration
2. feat/codex-msaf-compatibility - MSAF compatibility and bypass mode
3. feat/codex-websocket-hardening - WebSocket auth hardening and e2e tests

Test plan

• All pre-commit checks pass (ruff, mypy, format)
• 1081 unit/plugin tests pass
• Core adapter tests verify request preparation, template application, content-encoding handling
• Detection service tests verify header merging and fallback behavior

[Copilot]

Pull request overview

Integrates Codex v0.114.0 behaviors into the Codex plugin by refactoring request preparation (header/body handling, request template defaults, encoded-body passthrough), adding a first-pass WebSocket /responses handler, and tightening detection cache fallback handling.

Changes:

• Refactor CodexAdapter.prepare_provider_request to split header preparation, support encoded-body passthrough, and apply template defaults + input normalization.
• Add Codex /v1/responses WebSocket handler that bridges upstream SSE streaming to WebSocket messages and enrich /v1/models output.
• Improve detection cache resilience by selectively merging fallback headers/prompts and narrowing fallback exception types.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
ccproxy/plugins/codex/adapter.py	Splits header/body handling, supports content-encoding passthrough, applies request template + normalizes input message items.
ccproxy/plugins/codex/routes.py	Adds WebSocket /v1/responses + legacy WS route, CLI-model cache reading, and augments /v1/models response shape.
ccproxy/plugins/codex/detection_service.py	Adds content-encoding to ignored headers and introduces safe fallback loading/merging for headers/prompts.
tests/plugins/codex/unit/test_adapter.py	Adds unit coverage for encoded-body passthrough, content-encoding stripping for plain JSON, token field removal, and template defaults.
tests/plugins/codex/integration/test_codex_basic.py	Expands models endpoint assertions for added models field and expected slug/display_name.
tests/unit/plugins/test_codex_detection.py	Adds assertion that content-encoding is ignored by detection.

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[Copilot]

_make_websocket_terminal_event() always emits event type "response.completed" even when an error is present (status="failed"), and it omits fields (e.g., sequence_number) that are present on normal Responses streaming events. Clients and internal stream adapters typically use the event type/schema to detect failures/completion. Consider emitting a schema-consistent terminal event (include sequence_number, and use "response.failed" when error is set).