fix(#2767): pass paths via --files to gsd-sdk query commit + lint guard (#2781)

* fix(#2767): pass paths via --files to gsd-sdk query commit + lint guard

Workflows, agents, commands, and references passed file paths positionally
to `gsd-sdk query commit`, which silently appended them to the commit
subject and triggered the `.planning/` wholesale-stage fallback in
sdk/src/query/commit.ts:136. Regression of #733/#798.

Inserted `--files` before the path list at every site (81 invocations
across 50 files). Added tests/bug-2767-gsd-sdk-commit-files-flag.test.cjs
as a permanent lint that scans every shipped .md file and asserts each
`gsd-sdk query commit[-to-subrepo]` invocation either uses `--files` or
carries no path arguments.

Closes #2767

* test(#2767): replace source-grep with behavioral SDK test

The original test walked every shipped .md file and regex-tokenized
`gsd-sdk query commit` invocations to assert `--files` was present.
CONTRIBUTING.md prohibits this source-grep pattern.

Rewrite as behavioral SDK tests against `sdk/dist/cli.js` over a real
tmp git project (createTempGitProject helper). Cover both the
well-formed (`--files <paths>`) form — clean subject, exactly-staged
files, .planning/ left untouched — and the buggy positional form,
asserting the documented misbehavior (paths leak into subject + the
`.planning/` wholesale-stage fallback at commit.ts:136). Also asserts
`commit-to-subrepo` rejects when `--files` is omitted (commit.ts:258).

The doc-lint is retained as a supplementary defense-in-depth guard
since agent-prompt markdown invocations cannot be exercised end-to-end
— but it is no longer the primary contract.

* docs(#2767): correct contradictory --files guidance in zh-CN/en docs + fix test docstring

docs/zh-CN/references/git-planning-commit.md

@@ -4,12 +4,12 @@
 
 ## 通过 CLI 提交
 
-先传提交说明，再传文件路径（位置参数）。`commit` 不要使用 `--files`（该标志仅用于 `commit-to-subrepo`）。
+先传提交说明，然后用 `--files` 显式传入文件路径。`commit` 与 `commit-to-subrepo` 都应使用 `--files` 来声明要提交的路径。
 
 对 `.planning/` 文件始终使用此方式 —— 它会自动处理 `commit_docs` 与 gitignore 检查：
 
 ```bash
-gsd-sdk query commit "docs({scope}): {description}" .planning/STATE.md .planning/ROADMAP.md
+gsd-sdk query commit "docs({scope}): {description}" --files .planning/STATE.md .planning/ROADMAP.md
 ```
 
 如果 `commit_docs` 为 `false` 或 `.planning/` 被 gitignore，CLI 会返回 `skipped`（带原因）。无需手动条件检查。
@@ -19,7 +19,7 @@ gsd-sdk query commit "docs({scope}): {description}" .planning/STATE.md .planning
 将 `.planning/` 文件变更合并到上次提交：
 
 ```bash
-gsd-sdk query commit "" .planning/codebase/*.md --amend
+gsd-sdk query commit "" --files .planning/codebase/*.md --amend
 ```
 
 ## 提交消息模式