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>

Dockerfile

@@ -7,8 +7,6 @@ RUN go mod download
 COPY cmd/    ./cmd/
 COPY pkg/    ./pkg/
 
-# Tests run inside the build container — Gitea/act DinD makes mount-based
-# `docker run -v $PWD:/src` unreliable for native go test from the runner job.
 RUN go test -count=1 ./...
 
 ARG GIT_SHA=unknown
@@ -17,10 +15,14 @@ RUN CGO_ENABLED=0 go build -trimpath \
         -o /out/flock ./cmd/flock \
  && CGO_ENABLED=0 go build -trimpath \
         -ldflags="-s -w -X main.gitSHA=${GIT_SHA}" \
-        -o /out/flock-agent ./cmd/flock-agent
+        -o /out/flock-agent ./cmd/flock-agent \
+ && CGO_ENABLED=0 go build -trimpath \
+        -ldflags="-s -w -X main.gitSHA=${GIT_SHA}" \
+        -o /out/flock-installer ./cmd/flock-installer
 
 FROM alpine:3.21
-RUN apk add --no-cache iproute2 ca-certificates
-COPY --from=build /out/flock        /usr/local/bin/flock
-COPY --from=build /out/flock-agent  /usr/local/bin/flock-agent
+RUN apk add --no-cache iproute2 bird2 ca-certificates
+COPY --from=build /out/flock           /usr/local/bin/flock
+COPY --from=build /out/flock-agent     /usr/local/bin/flock-agent
+COPY --from=build /out/flock-installer /usr/local/bin/flock-installer
 ENTRYPOINT ["/usr/local/bin/flock-agent"]