fix(ci): meta-audit gate 冒烟化——补 starlette 依赖 + CI 不 gate all_passed

[frankiehot-tech]

背景

Meta-Audit Gate 已连续失败 run #248-252（每 5 分钟 1 次），是本次远程开源仓库健康度审计（2026-08-14）的 P0 项之一。

根因

1. 依赖缺失：src/maref/observability/otel_middleware.py 顶层 from starlette.middleware.base import ...，但 otel extras 未声明 starlette。CI 安装 .[dev] 时 ModuleNotFoundError 导致 meta_monitor 无法启动。
2. CI 语义错位：M0 audit_log / M3 report_freshness / M4 telemetry 依赖部署环境运行时数据；干净 CI runner 无数据源，all_passed 必然为 false，即使依赖修复后 gate 仍红。

修复

• pyproject.toml：otel extras 补 starlette>=0.37
• meta-audit-gate.yml：
  • install 补全 .[dev,otel,sidecar]
  • Run 步骤容忍运行时数据 gate 非零退出（记录到 stdout，不 gate）
  • Check 步骤改为冒烟验证：报告必须生成且 JSON 可解析，否则失败；M0-M4 状态仅作信息性输出
• 真实健康门禁由部署环境 run_loop (--daemon) 承担（CI 冒烟只验证"meta_monitor 可运行 + 报告可生成"）

验证

• 本地 python -m maref.observability.meta_monitor --single-run 在空环境（模拟 CI）可运行并生成报告
• 冒烟逻辑：报告存在且可解析 → exit 0；报告缺失 → exit 1 打印 stdout tail
• pre-push hook oss-check 放行

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