fix: skip default clone to avoid LFS failure

Woodpecker's default clone step fails when git-lfs isn't installed.
Using manual clone with alpine/git instead.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.woodpecker/pr.yml

@@ -2,11 +2,20 @@
 when:
   - event: pull_request
 
+skip_clone: true
+
 steps:
+  - name: clone
+    image: alpine/git
+    commands:
+      - git clone --depth=1 ${CI_REPO_CLONE_URL} .
+      - git checkout ${CI_COMMIT_SHA}
+
   - name: restore
     image: mcr.microsoft.com/dotnet/sdk:10.0-preview
     commands:
       - dotnet restore
+    depends_on: [clone]
 
   - name: build
     image: mcr.microsoft.com/dotnet/sdk:10.0-preview