ci(deploy): fetch full history + fallback when base sha unreachable

fetch-depth: 2 is too shallow — a batch push of 10 commits (like
Phase 1-6 commit chain) leaves github.event.before outside the
fetched range, so git diff returns empty and nothing deploys.

- Set fetch-depth: 0 (full history) so diff always has a reachable
  base.
- Added git cat-file -e check: even with full history, force-pushes
  or orphan base SHAs trigger a "deploy all" fallback instead of
  silently skipping.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.github/workflows/deploy.yml

@@ -40,8 +40,9 @@ jobs:
     steps:
       - uses: actions/checkout@v5
         with:
-          # diff 判斷需要前一個 commit
-          fetch-depth: 2
+          # 抓全部 history 以確保 github.event.before 可及
+          # (fetch-depth: 2 會在大批 commit push / force-push 時失效)
+          fetch-depth: 0
 
       - name: Enumerate & filter
         id: emit
@@ -95,10 +96,13 @@ jobs:
             # 也要連動 registry/components/{name}/ — 改 main.go 應該 redeploy .component-builds/{name}/
             base_sha="${{ github.event.before }}"
             head_sha="${{ github.sha }}"
-            # 若 base 為 0000...(首次 push)或 base 不可及,fallback 為全部
+            # 若 base 為 0000...(首次 push)或 base 在本地不可及,fallback 為全部
             if [[ -z "$base_sha" || "$base_sha" == "0000000000000000000000000000000000000000" ]]; then
               echo "No base sha, deploy all"
               targets=("${all_dirs[@]}")
+            elif ! git cat-file -e "$base_sha" 2>/dev/null; then
+              echo "Base sha $base_sha unreachable locally, deploy all"
+              targets=("${all_dirs[@]}")
             else
               # 取得 diff 的檔案路徑
               mapfile -t changed < <(git diff --name-only "$base_sha" "$head_sha" || true)