feat: add per-screenshot timing to profiling, fix stop sequence IndexError

- Track screenshot duration (avg/max/min ms) and total iteration duration
  per screen reader loop iteration in profiling.json
- Reset stop sequence index after match to prevent IndexError on extra
  keypresses

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: abrichr

openadapt_capture/recorder.py

@@ -762,6 +762,7 @@ def read_screen_events(
     terminate_processing: multiprocessing.Event,
     recording: Recording,
     started_event: threading.Event,
+    _screen_timing: list | None = None,
 ) -> None:
     """Read screen events and add them to the event queue.
 
@@ -773,6 +774,7 @@ def read_screen_events(
         terminate_processing: An event to signal the termination of the process.
         recording: The recording object.
         started_event: Event to set once started.
+        _screen_timing: If provided, append (screenshot_dur, total_dur) per iteration.
     """
     utils.set_start_time(recording.timestamp)
 
@@ -784,6 +786,7 @@ def read_screen_events(
     while not terminate_processing.is_set():
         t_start = time.perf_counter()
         screenshot = utils.take_screenshot()
+        t_screenshot = time.perf_counter()
         if screenshot is None:
             logger.warning("Screenshot was None")
             continue
@@ -797,6 +800,9 @@ def read_screen_events(
             sleep_time = min_interval - elapsed
             if sleep_time > 0:
                 time.sleep(sleep_time)
+        if _screen_timing is not None:
+            t_end = time.perf_counter()
+            _screen_timing.append((t_screenshot - t_start, t_end - t_start))
     logger.info("Done")
 
 
@@ -1410,6 +1416,7 @@ def record(
         terminate_processing = multiprocessing.Event()
     task_by_name = {}
     task_started_events = {}
+    _screen_timing = []  # per-iteration (screenshot_dur, total_dur) for profiling
 
     if config.RECORD_WINDOW_DATA:
         window_event_reader = threading.Thread(
@@ -1448,6 +1455,7 @@ def record(
             terminate_processing,
             recording,
             task_started_events.setdefault("screen_event_reader", threading.Event()),
+            _screen_timing,
         ),
     )
     screen_event_reader.start()
@@ -1759,6 +1767,7 @@ def join_tasks(task_names: list[str]) -> None:
             "browser": num_browser_events.value,
             "video": num_video_events.value,
         },
+        "screen_timing": {},
         "config": {
             "RECORD_VIDEO": config.RECORD_VIDEO,
             "RECORD_AUDIO": config.RECORD_AUDIO,
@@ -1771,6 +1780,19 @@ def join_tasks(task_names: list[str]) -> None:
         },
         "capture_dir": capture_dir,
     }
+    # Compute screen timing stats
+    if _screen_timing:
+        ss_durs = [t[0] for t in _screen_timing]
+        total_durs = [t[1] for t in _screen_timing]
+        _profile_data["screen_timing"] = {
+            "iterations": len(_screen_timing),
+            "screenshot_avg_ms": round(sum(ss_durs) / len(ss_durs) * 1000, 1),
+            "screenshot_max_ms": round(max(ss_durs) * 1000, 1),
+            "screenshot_min_ms": round(min(ss_durs) * 1000, 1),
+            "total_avg_ms": round(sum(total_durs) / len(total_durs) * 1000, 1),
+            "total_max_ms": round(max(total_durs) * 1000, 1),
+        }
+
     _profile_path = os.path.join(capture_dir, "profiling.json")
     try:
         import json as _json
@@ -1786,6 +1808,11 @@ def join_tasks(task_names: list[str]) -> None:
         for k, v in _profile_data["event_counts"].items():
             rate = v / _profile_duration if _profile_duration > 0 else 0
             print(f"  {k}: {v} events ({rate:.1f}/s)")
+        if _screen_timing:
+            st = _profile_data["screen_timing"]
+            print(f"  screenshot: avg={st['screenshot_avg_ms']}ms "
+                  f"max={st['screenshot_max_ms']}ms "
+                  f"min={st['screenshot_min_ms']}ms")
         print(f"Config: WINDOW_DATA={config.RECORD_WINDOW_DATA} "
               f"VIDEO={config.RECORD_VIDEO} "
               f"PLOT_PERF={config.PLOT_PERFORMANCE} "