Add repo-watcher-controller for polling remote Git refs

Introduces a fourth controller that watches GitRepository resources and
polls their remotes via git ls-remote on a configurable per-repo interval
(spec.pollInterval, defaulting to 30s). It auto-creates, updates, and
deletes GitBranch CRDs to reflect the actual state of the remote,
enabling fast detection of external pushes to trigger downstream sync.

Key changes:
- Add PollInterval field to GitRepositorySpec
- New pkg/reconciler/repowatcher with controller and reconciler
- New cmd/repo-watcher-controller binary
- CRD manifest updated for pollInterval
- Deployment manifest for the new controller
- Unit tests for ref filtering, naming, and poll interval logic
- CLAUDE.md updated with new controller docs and Go module workaround

https://claude.ai/code/session_01P7xfBqARU5DFS8QJ4uDPVj

pkg/apis/git/v1alpha1/zz_generated.deepcopy.go

@@ -6,6 +6,7 @@
 package v1alpha1
 
 import (
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	runtime "k8s.io/apimachinery/pkg/runtime"
 )
 
@@ -79,6 +80,11 @@ func (in *GitRepositorySpec) DeepCopyInto(out *GitRepositorySpec) {
 		*out = new(GitAuth)
 		(*in).DeepCopyInto(*out)
 	}
+	if in.PollInterval != nil {
+		in, out := &in.PollInterval, &out.PollInterval
+		*out = new(metav1.Duration)
+		**out = **in
+	}
 }
 
 // DeepCopy is an autogenerated deepcopy function, copying the receiver, creating a new GitRepositorySpec.