slice 8B.2 (agent): emit snapshotted phase at storage-snapshot moment (v0.13.0)

BackupRunner.BackupWithSnapshotHook tails the task log for the 'create storage
snapshot' marker (snapshot mode only) and fires onSnapshot once; localapi flips
/backup/status to 'snapshotted' before 'done' so the controller resumes early.
Phase 0 validated on PVE 9.2.2: marker confirmed, downtime ~24s->~1s (934MB).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/backup/runner_snapshot_test.go

@@ -0,0 +1,72 @@
+package backup
+
+import (
+	"context"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"gitea.dooplex.hu/admin/felhom-agent/internal/proxmox"
+)
+
+// 8B.2: in snapshot mode, the runner fires onSnapshot when the storage-snapshot marker appears in
+// the task log — mid-backup, before completion.
+func TestBackupWithSnapshotHook_FiresOnMarker(t *testing.T) {
+	old := snapshotWatchInterval
+	snapshotWatchInterval = 2 * time.Millisecond
+	defer func() { snapshotWatchInterval = old }()
+
+	api := &fakeBackupAPI{
+		vzdumpUPID: "UPID:backup",
+		waitGate:   make(chan struct{}), // hold the backup open so the watcher gets to poll
+		logLines:   []string{"INFO: backup mode: snapshot", "INFO: create storage snapshot 'vzdump'"},
+		content:    []proxmox.StorageContent{{VolID: "local:backup/vzdump-lxc-9001-x", Content: "backup", VMID: 9001, Size: 100, CTime: 1}},
+	}
+	r := NewBackupRunner(api, "local", "", "", quiet())
+
+	var fired int32
+	done := make(chan struct{})
+	go func() {
+		_, _ = r.BackupWithSnapshotHook(context.Background(), 9001, func() { atomic.StoreInt32(&fired, 1) })
+		close(done)
+	}()
+
+	// the watcher should fire onSnapshot well before we release the backup
+	deadline := time.Now().Add(time.Second)
+	for time.Now().Before(deadline) && atomic.LoadInt32(&fired) == 0 {
+		time.Sleep(2 * time.Millisecond)
+	}
+	if atomic.LoadInt32(&fired) != 1 {
+		t.Fatal("onSnapshot did not fire on the storage-snapshot marker")
+	}
+	close(api.waitGate) // let the backup complete
+	<-done
+}
+
+// Stop/downgraded mode → no storage-snapshot marker → onSnapshot never fires (the 8B.2 fallback).
+func TestBackupWithSnapshotHook_StopMode_NeverFires(t *testing.T) {
+	old := snapshotWatchInterval
+	snapshotWatchInterval = 2 * time.Millisecond
+	defer func() { snapshotWatchInterval = old }()
+
+	api := &fakeBackupAPI{
+		vzdumpUPID: "UPID:backup",
+		waitGate:   make(chan struct{}),
+		logLines:   []string{"INFO: backup mode: stop"}, // downgraded; no snapshot marker
+		content:    []proxmox.StorageContent{{VolID: "local:backup/vzdump-lxc-9001-x", Content: "backup", VMID: 9001, Size: 100, CTime: 1}},
+	}
+	r := NewBackupRunner(api, "local", "", "", quiet())
+
+	var fired int32
+	done := make(chan struct{})
+	go func() {
+		_, _ = r.BackupWithSnapshotHook(context.Background(), 9001, func() { atomic.StoreInt32(&fired, 1) })
+		close(done)
+	}()
+	time.Sleep(40 * time.Millisecond) // the watcher polls several times + sees stop mode → returns
+	if atomic.LoadInt32(&fired) != 0 {
+		t.Fatal("onSnapshot fired in stop mode (must not)")
+	}
+	close(api.waitGate)
+	<-done
+}