test: fix section 6 map unpack; warmup=30; add p95 to timing stats

- Section 6 _on_live_sample: buf.map() returns (ok, map_info) tuple;
  accessing .size on the tuple caused AttributeError for every frame
  (22 tracebacks in log). Fixed to unpack properly.

- Section 8 WARMUP raised from 5 to 30 frames (~1.25 s) so cold-DRM
  DMA setup, network buffer fill, and lazy texture init all complete
  before stats are recorded. Eliminates the 36ms first-upload spike
  from post-warmup measurements.

- _stat() now shows mean / p95 / max so isolated spikes are visible
  without inflating the headline figure.

tests/test_video_playback_device.py

@@ -267,10 +267,10 @@ else:
             sample = sink.emit("pull-sample")
             if sample:
                 buf = sample.get_buffer()
-                info = buf.map(Gst.MapFlags.READ)
-                if info.size > 0:
+                ok_m, map_info = buf.map(Gst.MapFlags.READ)
+                if ok_m and map_info.size > 0:
                     live_frames += 1
-                buf.unmap(info)
+                buf.unmap(map_info)
             return Gst.FlowReturn.OK
 
         vsink.connect("new-sample", _on_live_sample)
@@ -593,7 +593,7 @@ else:
         print("  (close window with Escape or Q, or wait for timeout)\n")
 
         # ── SDL render loop (runs on main thread) ───────────────────────────
-        WARMUP = 5
+        WARMUP = 30   # skip ~1.25 s of frames to let DRM, network and texture init settle
         deadline8 = time.monotonic() + SDL8_SECONDS
         frame_n = 0
 
@@ -699,10 +699,13 @@ else:
             if not samples_us:
                 print(f"  {label:38s}: no samples")
                 return
-            mn = statistics.mean(samples_us)
-            mx = max(samples_us)
+            mn  = statistics.mean(samples_us)
+            mx  = max(samples_us)
             pct = mn / budget * 100
-            print(f"  {label:38s}: mean {mn:6.0f} µs  max {mx:6.0f} µs  ({pct:.1f}% budget)")
+            # p95: sort and take the 95th-percentile value to filter outlier spikes
+            sorted_s = sorted(samples_us)
+            p95 = sorted_s[int(len(sorted_s) * 0.95)]
+            print(f"  {label:38s}: mean {mn:6.0f} µs  p95 {p95:6.0f} µs  max {mx:6.0f} µs  ({pct:.1f}% budget)")
 
         _stat("memmove (GStreamer thread)",     fs.memmove_us[WARMUP:] if len(fs.memmove_us) > WARMUP else fs.memmove_us)
         _stat("SDL_UpdateNVTexture (main thread)",  fs.upload_us)