fix(tmux): add debounce delay between paste and Enter

Fixes race condition where Enter key arrives before paste is fully
processed, causing workers to sit idle at prompts.

- SendKeys now uses 100ms default debounce
- New SendKeysDebounced allows configurable delay
- Inject scales delay 100-500ms based on message size

Closes: gt-w3bu

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/tmux/tmux.go

@@ -110,11 +110,23 @@ func (t *Tmux) ListSessions() ([]string, error) {
 
 // SendKeys sends keystrokes to a session and presses Enter.
 // Always sends Enter as a separate command for reliability.
+// Uses a debounce delay between paste and Enter to ensure paste completes.
 func (t *Tmux) SendKeys(session, keys string) error {
+	return t.SendKeysDebounced(session, keys, 100) // 100ms default debounce
+}
+
+// SendKeysDebounced sends keystrokes with a configurable delay before Enter.
+// The debounceMs parameter controls how long to wait after paste before sending Enter.
+// This prevents race conditions where Enter arrives before paste is processed.
+func (t *Tmux) SendKeysDebounced(session, keys string, debounceMs int) error {
 	// Send text using literal mode (-l) to handle special chars
 	if _, err := t.run("send-keys", "-t", session, "-l", keys); err != nil {
 		return err
 	}
+	// Wait for paste to be processed
+	if debounceMs > 0 {
+		time.Sleep(time.Duration(debounceMs) * time.Millisecond)
+	}
 	// Send Enter separately - more reliable than appending to send-keys
 	_, err := t.run("send-keys", "-t", session, "Enter")
 	return err