feat: harden concurrency scheduling and task watchdog

pkg/tools/tracked_output.go

@@ -0,0 +1,43 @@
+package tools
+
+import (
+	"bytes"
+	"sync"
+	"sync/atomic"
+)
+
+// trackedOutput is a thread-safe writer+buffer pair used by command progress checks.
+type trackedOutput struct {
+	mu   sync.Mutex
+	buf  bytes.Buffer
+	size atomic.Int64
+}
+
+func (t *trackedOutput) Write(p []byte) (int, error) {
+	if t == nil {
+		return 0, nil
+	}
+	t.mu.Lock()
+	n, err := t.buf.Write(p)
+	t.mu.Unlock()
+	if n > 0 {
+		t.size.Add(int64(n))
+	}
+	return n, err
+}
+
+func (t *trackedOutput) Len() int {
+	if t == nil {
+		return 0
+	}
+	return int(t.size.Load())
+}
+
+func (t *trackedOutput) String() string {
+	if t == nil {
+		return ""
+	}
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	return t.buf.String()
+}