GitLab

- 接入 gpt-5.4-mini/nano 模型识别与规范化，补充默认模型列表
- 增加 gpt-5.4-mini/nano 输入/缓存命中/输出价格与计费兜底逻辑
- 同步前端模型白名单与 OpenCode 配置
- 补充 service tier(priority/flex) 计费回归测试

- 接入 gpt-5.4-mini/nano 模型识别与规范化，补充默认模型列表
- 增加 gpt-5.4-mini/nano 输入/缓存命中/输出价格与计费兜底逻辑
- 同步前端模型白名单与 OpenCode 配置
- 补充 service tier(priority/flex) 计费回归测试

OAuth upstreams (ChatGPT) reject requests containing role:"system" in
the input array with HTTP 400 "System messages are not allowed". Extract
such items before forwarding and merge their content into the top-level
instructions field, prepending to any existing value.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

The ChatGPT backend-api codex/responses endpoint requires `input` to be
an array, but the OpenAI Responses API spec allows it to be a plain string.
When a client sends a string input, sub2api now converts it to the expected
message array format. Empty/whitespace-only strings become an empty array
to avoid triggering a 400 "Input must be a list" error.

- 接入 gpt-5.4 模型识别与规范化，补充默认模型列表
- 增加 gpt-5.4 输入/缓存命中/输出价格与计费兜底逻辑
- 同步前端模型白名单与 OpenCode 上下文窗口（1050000/128000）
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
(cherry picked from commit 924476dcac6181cd0f3ee731ec7b73672ff03793)

Key changes:
- Upgrade model mapping: Opus 4.5 → Opus 4.6-thinking with precise matching
- Unified rate limiting: scope-level → model-level with Redis snapshot sync
- Load-balanced scheduling by call count with smart retry mechanism
- Force cache billing support
- Model identity injection in prompts with leak prevention
- Thinking mode auto-handling (max_tokens/budget_tokens fix)
- Frontend: whitelist mode toggle, model mapping validation, status indicators
- Gemini session fallback with Redis Trie O(L) matching
- Ops: enhanced concurrency monitoring, account availability, retry logic
- Migration scripts: 049-051 for model mapping unification

移除不再需要的 setupCodexCache 调用与辅助函数（已不再回源/读写缓存）

- 不再从 GitHub 拉取 opencode codex_header.txt\n- 删除 ~/.opencode 缓存与异步刷新逻辑\n- 所有 instructions 统一使用内置 codex_cli_instructions.md

- 修改 applyCodexOAuthTransform 函数签名，增加 isCodexCLI 参数
- 移除 && !isCodexCLI 条件，对所有 OAuth 请求统一处理
- 新增 applyInstructions/applyCodexCLIInstructions/applyOpenCodeInstructions 辅助函数
- 新增 isInstructionsEmpty 函数检查 instructions 字段是否为空
- 添加 Codex CLI 和非 Codex CLI 场景的测试用例

逻辑说明：
- Codex CLI + 有 instructions: 保持不变
- Codex CLI + 无 instructions: 补充 opencode 指令
- 非 Codex CLI: 使用 opencode 指令覆盖

- codex_transform: 过滤无效工具，支持 Responses-style 和 ChatCompletions-style 格式
- tool_corrector: 添加 fetch 工具映射，修正 bash/edit 参数命名规范

避免上游 Store 必须为 false 的错误

仅在缺失或 true 时写回 store

测试: go test ./internal/service -run TestApplyCodexOAuthTransform

测试: make test-backend（golangci-lint 已单独执行）

    openai_codex_transform_test.go:36、backend/internal/service/
    openai_codex_transform_test.go:89、backend/internal/service/
    openai_codex_transform_test.go:104）。

完善 function_call_output 续链校验与引用匹配
续链场景强制 store=true，过滤 input 时避免副作用
补充续链判断与过滤相关单元测试

测试: go test ./...