fix(vcs): resolve shelf files against their owning repository (#919)

Root cause: shelved file paths are relative to the repository they were shelved from, but Compare with Local, Show Diff, navigation and Unshelve joined them to the selected VCS root. In a project folder that is not itself a repository (or holds several), the local file was not found and Compare with Local stayed disabled. Shelves now record their repository (older shelves fall back to the primary repository), imported patches record the current one, and every shelf action resolves paths against it, with Windows separators handled. Stash and Apply Patch already kept their repository.

Fixes #875

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/platform/locales/text/zh.json

@@ -5515,5 +5515,7 @@
   "App labels, modules or dotted test paths; empty runs every test": "应用标签、模块或以点分隔的测试路径；留空则运行全部测试",
   "Settings module": "设置模块",
   "Passed as --settings; empty keeps DJANGO_SETTINGS_MODULE or the default in manage.py": "作为 --settings 传入；留空则沿用 DJANGO_SETTINGS_MODULE 或 manage.py 中的默认值",
-  "e.g. --keepdb --parallel": "例如 --keepdb --parallel"
+  "e.g. --keepdb --parallel": "例如 --keepdb --parallel",
+  "select files in a git repository to shelve": "请选择 Git 仓库中的文件以搁置更改",
+  "select files from a single git repository to shelve": "请一次只选择同一个 Git 仓库中的文件以搁置更改"
 }