v0.5.0-rc1: slice 5 Phase A — storage observe/report + watchdog (read-only, live)

Fill the slice-3 storage_targets stub and add the fast-poll storage watchdog.
Read-only this phase; the host-root surface (mounts/SMART/grow/destructive gate)
is Phase B. Hub-owned desired manifest is slice 10, so reconcile against it is
built-but-unfed.

- internal/storage: StorageTarget wire contract, durable_id derivation per type,
  HostReader seam (procfs/sysfs, root-free), Observer (storage_targets from
  ListStorage/NodeStorage + host reads, lvmthin thin-pool fill), and the watchdog
  (third daemon goroutine; debounced out-of-band report on a known target's
  attach/disconnect transition).
- proxmox.Storage: additive parse-only config fields (durable_id sources).
- collector StorageObserver seam; Loop.SetTrigger out-of-band report; daemon runs
  the watchdog as a third goroutine; StorageConfig knobs.
- cross-repo golden kept byte-identical with felhom.eu/hub; bidirectional key-set test.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/hub/collect_test.go

@@ -20,6 +20,41 @@ func newTestNodeStatus() proxmox.NodeStatus {
 	return ns
 }
 
+// fakeObserver is a StorageObserver returning fixed targets (or an error).
+type fakeObserver struct {
+	targets []StorageTarget
+	err     error
+}
+
+func (f fakeObserver) Observe(context.Context) ([]StorageTarget, error) { return f.targets, f.err }
+
+func TestCollect_StorageTargetsFromObserver(t *testing.T) {
+	px := &fakePx{node: "n", ns: newTestNodeStatus()}
+	obs := fakeObserver{targets: []StorageTarget{
+		{Name: "local-lvm", Type: StorageTypeLVMThin, State: StorageStateAttached, Reachable: true},
+	}}
+	c := NewCollector(px, fakeProber{status: "active"}, obs, "h", "0.5.0", quietLogger())
+	r, err := c.Collect(context.Background())
+	if err != nil {
+		t.Fatalf("Collect: %v", err)
+	}
+	if len(r.StorageTargets) != 1 || r.StorageTargets[0].Name != "local-lvm" {
+		t.Fatalf("storage targets = %+v", r.StorageTargets)
+	}
+}
+
+func TestCollect_StorageObserverErrorDegradesToEmpty(t *testing.T) {
+	px := &fakePx{node: "n", ns: newTestNodeStatus()}
+	c := NewCollector(px, fakeProber{status: "active"}, fakeObserver{err: errors.New("proxmox down")}, "h", "0.5.0", quietLogger())
+	r, err := c.Collect(context.Background())
+	if err != nil {
+		t.Fatalf("a storage observe error must not sink the heartbeat: %v", err)
+	}
+	if r.StorageTargets == nil || len(r.StorageTargets) != 0 {
+		t.Errorf("storage targets must degrade to empty non-nil, got %+v", r.StorageTargets)
+	}
+}
+
 func TestCollect_HostAndGuests(t *testing.T) {
 	px := &fakePx{
 		node: "demo-felhom",
@@ -29,7 +64,7 @@ func TestCollect_HostAndGuests(t *testing.T) {
 		},
 		cfg: map[int]proxmox.GuestConfig{100: {Cores: 2, Memory: 2048}},
 	}
-	c := NewCollector(px, fakeProber{status: "active"}, "demo-host-01", "0.3.0", quietLogger())
+	c := NewCollector(px, fakeProber{status: "active"}, nil, "demo-host-01", "0.3.0", quietLogger())
 	r, err := c.Collect(context.Background())
 	if err != nil {
 		t.Fatalf("Collect: %v", err)
@@ -69,7 +104,7 @@ func TestCollect_GuestConfigFailureKeepsStatusOmitsSpec(t *testing.T) {
 		cfg:    map[int]proxmox.GuestConfig{100: {Cores: 2}},
 		cfgErr: map[int]error{200: errors.New("config read failed")},
 	}
-	c := NewCollector(px, fakeProber{status: "active"}, "h", "0.3.1", quietLogger())
+	c := NewCollector(px, fakeProber{status: "active"}, nil, "h", "0.3.1", quietLogger())
 	r, err := c.Collect(context.Background())
 	if err != nil {
 		t.Fatalf("a per-guest failure must NOT fail the whole report: %v", err)
@@ -90,7 +125,7 @@ func TestCollect_GuestConfigFailureKeepsStatusOmitsSpec(t *testing.T) {
 
 func TestCollect_NodeStatusFailureIsHardError(t *testing.T) {
 	px := &fakePx{node: "n", nsErr: errors.New("proxmox down")}
-	c := NewCollector(px, fakeProber{status: "active"}, "h", "0.3.0", quietLogger())
+	c := NewCollector(px, fakeProber{status: "active"}, nil, "h", "0.3.0", quietLogger())
 	if _, err := c.Collect(context.Background()); err == nil {
 		t.Fatal("NodeStatus failure must be a hard error (no useful report)")
 	}
@@ -98,7 +133,7 @@ func TestCollect_NodeStatusFailureIsHardError(t *testing.T) {
 
 func TestCollect_CloudflaredProbeErrorIsUnknown(t *testing.T) {
 	px := &fakePx{node: "n", ns: newTestNodeStatus()}
-	c := NewCollector(px, fakeProber{err: errors.New("no systemctl")}, "h", "0.3.0", quietLogger())
+	c := NewCollector(px, fakeProber{err: errors.New("no systemctl")}, nil, "h", "0.3.0", quietLogger())
 	r, err := c.Collect(context.Background())
 	if err != nil {
 		t.Fatalf("cloudflared failure must not be fatal: %v", err)