Wire the composition root: flags, providers, runnables, manifests, samples, docs

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

config/samples/proxy_kubernetes.yaml

@@ -0,0 +1,14 @@
+# A Managed proxy backed by the kubernetes-pod provider: the operator runs
+# a real Squid pod in this cluster. This is the local-dev/CI sample — pods
+# share the cluster's egress IP, so it exercises the full lifecycle but
+# does not provide a distinct egress path (use the gcp provider for that).
+apiVersion: crawl.example.com/v1alpha1
+kind: Proxy
+metadata:
+  name: proxy-kubernetes-sample
+spec:
+  mode: Managed
+  provider: kubernetes
+  attributes:
+    geo: local
+    purpose: crawl