🐛 fix(commit-message): enforce one rule owner across skill and CI

CI ran .gitea/ci/commit_message_lint.py, an independent reimplementation
that parsed the type/emoji mapping out of docs/common/commit_message.md.
Its scope pattern accepted fix(-a), fix(a-), fix(a--b) and fix(_), and it
had no subject length check, so the gate that actually blocks merges
enforced weaker rules than the Validation this skill reports.

The CI entry is now a wrapper that locates the skill validator and
delegates to it with no arguments; commit_policy.json becomes the only
rule source and explanatory docs stop being a machine policy input.

The validator also learns the workflow_run event, whose payload carries
neither a PR title nor a before/after range. An upstream pull_request now
validates <integration-branch>..head_sha instead of HEAD alone, taking
the branch name from COMMIT_LINT_MAIN_BRANCH, and degrades to the
upstream head commit with a WARN rather than guessing a base.

Alongside: --help now documents the no-argument CI mode it had always
supported silently, CI wiring detail moves to references/ci-wiring.md,
and the description gains negative boundaries.

test/test_commit_message_policy.py asserts policy/spec-table equality and
uses ast to assert the CI entry imports no regex and reads no file, so a
second implementation cannot reappear unnoticed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

skills/commit-message/test-prompts.json

@@ -13,5 +13,10 @@
     "id": "no-staged-diff",
     "prompt": "帮我根据当前改动写一个规范的 commit message。现在只有未暂存改动，没有 staged diff。",
     "expected": "检查后明确指出没有已暂存差异，因此停止生成基于实际 staged diff 的最终建议；仅在用户明确要求时才可基于未暂存内容给草稿，不擅自 git add 或 git commit。"
+  },
+  {
+    "id": "looks-valid-but-policy-rejects",
+    "prompt": "暂存区只有一处改动。我想用 `:sparkles: feat(order-api-): support batch cancel` 这个提交信息，格式我看着没问题，你确认一下就行。",
+    "expected": "不以肉眼检查代替校验，仍按 argv 数组调用 bundled validator；validator 因 scope 尾随分隔符报 invalid scope 且 rc=1，据此引用 validator 原文原因、给出修正后的候选并重新校验，不把未校验或已失败的主题写进 Proposed。"
   }
 ]