fix(rss): detect empty or HTML responses feedparser treats as non-bozo (#36)

[1012839419a-alt]

Closes #36

问题

feedparser 对空响应体 / HTML 错误页返回 bozo=False, entries=[]，与合法空 feed 无法区分（已用 feedparser 6.0.12 实测复现：空 body → bozo=False, version=None；HTML 错误页 → bozo=False, version=''）。采集表现为"成功的空 feed"，无结构化 error_type 到达 control recorder，SCHEMA_DRIFT 传感器不触发。

修复

backend/channels/rss_channel.py：

• 新增 _parsed_version() / _non_feed_response() 辅助函数
• collect() 与 fetch() 在既有 W1 bozo 分支之后，检测"零条目且 feedparser 未识别任何 feed 格式（version 为空/None）"的响应，显式失败并携带 error_type="ParseError"（error_kinds.py 映射 SCHEMA_DRIFT）
• 保守设计：合法空 feed（rss20/atom10，version 非空）不受影响；部分解析出条目的 feed 不受影响
• body-shape 启发式（feedparser version 字段作为判据）已在辅助函数 docstring 记录

与 WIRING_GAP_LEDGER W1（#35 / #60 已修）互补：W1 覆盖 bozo=True 的解析失败，本 PR 覆盖 bozo=False 的响应质量问题，两者都是 SCHEMA_DRIFT 链路的输入。

测试

• tests/unit/channels/test_rss_channel_schema_drift.py +4：HTML 错误页 / 空 body / 非 feed 合法 XML → ParseError→SCHEMA_DRIFT；合法空 feed → 成功
• tests/unit/channels/test_rss_fetch.py +3：fetch 路径 HTML / 空 body → ChannelFetchError(ParseError)；合法空 feed → 成功
• pytest tests/unit/channels/ tests/unit/test_workflow_rss_source_executor.py：285 passed
• ruff check：通过

[repowise-bot]

⚠️ Health of changed files: 6.1 → 6.0 (-0.1)
_{⚠️ Change risk: moderate, riskier than 58% of this repo's commits.}

📋 At a glance
2 files changed health · 3 hotspots touched · 4 new findings introduced · 2 files with recent fix history.

Files & modules (2)

• backend (1 file)
  • backend/channels/rss_channel.py
• tests (2 files)
  • .../channels/test_rss_channel_schema_drift.py
  • .../channels/test_rss_fetch.py

✅ Health gate: passed

📌 Before you merge

• Run .../channels/test_rss_channel.py, .../channels/test_rss_channel_entries.py, .../channels/test_rss_channel_errors.py: they import the changed files

🔎 More signals (2)

🗺️ Change map

flowchart LR
  subgraph PR ["Changed in this PR (1 with dependents)"]
    f_backend_channels_rss_channel_py["backend/channels/rss_channel.py 🔥"]:::changed
  end
  f_backend_channels_api_channel_py["backend/channels/api_channel.py"]
  f_backend_channels_rss_channel_py --> f_backend_channels_api_channel_py
  f_backend_channels_registry_py["backend/channels/registry.py"]
  f_backend_channels_rss_channel_py --> f_backend_channels_registry_py
  f_backend_workflow_rss_source_executor_py["backend/workflow/rss_source_executor.py"]
  f_backend_channels_rss_channel_py --> f_backend_workflow_rss_source_executor_py
  t_tests_unit_channels_test_rss_channel_py(["✅ .../channels/test_rss_channel.py"]):::guard
  t_tests_unit_channels_test_rss_channel_py -.-> f_backend_channels_rss_channel_py
  classDef changed fill:#dbeafe,stroke:#1d4ed8,color:#1e3a5f
  classDef warn fill:#fef3c7,stroke:#b45309,color:#78350f
  classDef guard fill:#dcfce7,stroke:#15803d,color:#14532d

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_{Solid arrows: code that imports the changed files (3 direct dependents, from the last indexed snapshot). Dashed: history/tests.}

🔥 Hotspots touched (3)

• .../channels/test_rss_channel_schema_drift.py: 1 commits/90d, 0 dependents · primary owner: 2233admin (100%)
• .../channels/test_rss_fetch.py: 7 commits/90d, 0 dependents · primary owner: Curry (90%)
• backend/channels/rss_channel.py: 9 commits/90d, 11 dependents · primary owner: Curry (61%)

👀 Suggested reviewers @2233admin

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📥 Commits

Reviewing files that changed from the base of the PR and between 94ab53d and c2487ea.

📒 Files selected for processing (3)

• backend/channels/rss_channel.py
• tests/unit/channels/test_rss_channel_schema_drift.py
• tests/unit/channels/test_rss_fetch.py

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