Implement PVC-backed Git workspace cache (design-pvc-workspace.md)

Add pkg/workspace.Manager that provides Acquire/Release semantics for Git
repos. When GIT_CACHE_DIR is set and a GitRepository has spec.cache.enabled,
controllers use on-disk bare clones with incremental fetch; otherwise they
fall back to the existing in-memory clone behavior.

Key changes:
- New pkg/workspace package with Manager, Workspace, GC, Deepen, and
  context-based injection (WithManager/GetManager)
- GitRepository API gains spec.cache (CacheConfig) and status.cache
  (CacheStatus) with deepcopy and CRD schema updates
- Push, sync, and resolver reconcilers now use workspace.Acquire/Release
  instead of inline memory.NewStorage + git.CloneContext
- Shallow clone by default; sync/resolver deepen as needed for merge-base
- New Prometheus metrics: workspace_acquire_duration_seconds,
  workspace_cache_hit_total, workspace_cache_miss_total
- Deployment manifests include commented-out PVC configuration
- Comprehensive unit tests for workspace package (21 tests)
- E2E tests for cache-free and cache-enabled push flows

https://claude.ai/code/session_01NULGxaCLPMT1yDVEAsffc5

pkg/reconciler/sync/controller.go

@@ -18,6 +18,7 @@ import (
 	gitv1alpha1 "github.com/imjasonh/git-k8s/pkg/apis/git/v1alpha1"
 	gitclient "github.com/imjasonh/git-k8s/pkg/client"
 	"github.com/imjasonh/git-k8s/pkg/reconciler/internal"
+	"github.com/imjasonh/git-k8s/pkg/workspace"
 )
 
 var (
@@ -52,6 +53,7 @@ func NewController(ctx context.Context, cmw configmap.Watcher) *controller.Impl
 	r := &Reconciler{
 		dynamicClient: dynClient,
 		gitClient:     gitClient,
+		workspaces:    workspace.GetManager(ctx),
 	}
 
 	impl := controller.NewContext(ctx, internal.NewReconciler(