M2: netlink, IPAM/handler wiring, BIRD sidecar, CNI installer

Code (Linux build, with no-op stubs for macOS dev):
- pkg/agent/netns_linux.go: ensureVeth → host-side configure (addrgenmode
  none, fe80::1/64, proxy_arp, forwarding) → move peer to pod ns →
  configure pod side (addr, default route via fe80::1, v4 169.254.1.1
  on-link gateway) → host /128 + /32 routes. Idempotent.
- pkg/agent/hostiface.go: deterministic host iface name flock<8hex> from
  FNV-1a-32(containerID).
- pkg/agent/annotations.go: parse flock.fritzlab.net/{ipv6,ipv4,cidr6,
  cidr4,ip-algo,anycast} with design-doc defaults; ParseCNIArgs for the
  K8S_POD_* keys kubelet sets.
- pkg/agent/podinfo.go: shared informer scoped to spec.nodeName==NODE,
  WaitForPod helper for ADD-vs-informer-sync race.
- pkg/agent/handlers.go: PodHandler does
    cache lookup → annotations → IPAM → store(pending) → SetupFunc →
    store(committed) → Result. Idempotent on retry. Del symmetric.
- pkg/routing/bird/config.go: text/template render with stable ordering;
  golden tests for host001 + anycast injection + sort stability.
- pkg/agent/bird.go: writes /etc/flock/bird/bird.conf, debounces 500ms,
  execs `birdc -s /run/flock/bird.ctl configure`. Installs blackhole
  kernel routes for the node summary CIDRs so BIRD's protocol kernel
  imports them.
- pkg/agent/runtime_linux.go: at startup, waits up to 60s for the per-
  node NodeConfig, reconciles committed allocations into IPAM.used,
  garbage-collects pending entries, builds PodHandler, swaps RPC
  handlers in.
- cmd/flock-installer: init-container binary that copies /opt/cni/bin/
  flock and writes 01-flock.conflist (lex-first so kubelet picks it
  over Calico's 10-calico.conflist on flock-labeled nodes).

Deploy:
- Dockerfile: alpine + iproute2 + bird2; multi-binary image.
- deploy/daemonset.yaml: install-cni init container; bird sidecar
  sharing /etc/flock/bird + /run/flock with the agent; ConfigMap-seeded
  bootstrap bird.conf so the sidecar boots before the agent renders.
  Privileged on flock-agent + install-cni; bird sidecar uses
  NET_ADMIN/RAW only.
- RBAC: pods + networkpolicies get/list/watch (the latter is reserved
  for M8 — harmless to grant now).

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

go.mod

@@ -4,6 +4,9 @@ go 1.26.1
 
 require (
 	github.com/containernetworking/cni v1.3.0
+	github.com/containernetworking/plugins v1.9.1
+	github.com/vishvananda/netlink v1.3.1
+	k8s.io/api v0.36.0
 	k8s.io/apimachinery v0.36.0
 	k8s.io/client-go v0.36.0
 )
@@ -26,7 +29,7 @@ require (
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
 	github.com/spf13/pflag v1.0.9 // indirect
-	github.com/vishvananda/netns v0.0.4 // indirect
+	github.com/vishvananda/netns v0.0.5 // indirect
 	github.com/x448/float16 v0.8.4 // indirect
 	go.yaml.in/yaml/v2 v2.4.3 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
@@ -40,7 +43,6 @@ require (
 	gopkg.in/evanphx/json-patch.v4 v4.13.0 // indirect
 	gopkg.in/inf.v0 v0.9.1 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
-	k8s.io/api v0.36.0 // indirect
 	k8s.io/klog/v2 v2.140.0 // indirect
 	k8s.io/kube-openapi v0.0.0-20260317180543-43fb72c5454a // indirect
 	k8s.io/utils v0.0.0-20260210185600-b8788abfbbc2 // indirect