feat(demo): add HUD effect, resize handling, and tests

- Add HUD effect plugin showing FPS, effect name, intensity bar, pipeline
- Add pygame window resize handling (VIDEORESIZE event)
- Move HUD to end of chain so it renders on top
- Fix monitor stats API (returns dict, not object)
- Add tests/test_hud.py for HUD effect verification

tests/test_hud.py

@@ -0,0 +1,107 @@
+
+from engine.effects.performance import PerformanceMonitor, set_monitor
+from engine.effects.types import EffectContext
+
+
+def test_hud_effect_adds_hud_lines():
+    """Test that HUD effect adds HUD lines to the buffer."""
+    from effects_plugins.hud import HudEffect
+
+    set_monitor(PerformanceMonitor())
+
+    hud = HudEffect()
+    hud.config.params["display_effect"] = "noise"
+    hud.config.params["display_intensity"] = 0.5
+
+    ctx = EffectContext(
+        terminal_width=80,
+        terminal_height=24,
+        scroll_cam=0,
+        ticker_height=24,
+        mic_excess=0.0,
+        grad_offset=0.0,
+        frame_number=0,
+        has_message=False,
+        items=[],
+    )
+
+    buf = [
+        "A" * 80,
+        "B" * 80,
+        "C" * 80,
+    ]
+
+    result = hud.process(buf, ctx)
+
+    assert len(result) >= 3, f"Expected at least 3 lines, got {len(result)}"
+
+    first_line = result[0]
+    assert "MAINLINE DEMO" in first_line, (
+        f"HUD not found in first line: {first_line[:50]}"
+    )
+
+    second_line = result[1]
+    assert "EFFECT:" in second_line, f"Effect line not found: {second_line[:50]}"
+
+    print("First line:", result[0])
+    print("Second line:", result[1])
+    if len(result) > 2:
+        print("Third line:", result[2])
+
+
+def test_hud_effect_shows_current_effect():
+    """Test that HUD displays the correct effect name."""
+    from effects_plugins.hud import HudEffect
+
+    set_monitor(PerformanceMonitor())
+
+    hud = HudEffect()
+    hud.config.params["display_effect"] = "fade"
+    hud.config.params["display_intensity"] = 0.75
+
+    ctx = EffectContext(
+        terminal_width=80,
+        terminal_height=24,
+        scroll_cam=0,
+        ticker_height=24,
+        mic_excess=0.0,
+        grad_offset=0.0,
+        frame_number=0,
+        has_message=False,
+        items=[],
+    )
+
+    buf = ["X" * 80]
+    result = hud.process(buf, ctx)
+
+    second_line = result[1]
+    assert "fade" in second_line, f"Effect name 'fade' not found in: {second_line}"
+
+
+def test_hud_effect_shows_intensity():
+    """Test that HUD displays intensity percentage."""
+    from effects_plugins.hud import HudEffect
+
+    set_monitor(PerformanceMonitor())
+
+    hud = HudEffect()
+    hud.config.params["display_effect"] = "glitch"
+    hud.config.params["display_intensity"] = 0.8
+
+    ctx = EffectContext(
+        terminal_width=80,
+        terminal_height=24,
+        scroll_cam=0,
+        ticker_height=24,
+        mic_excess=0.0,
+        grad_offset=0.0,
+        frame_number=0,
+        has_message=False,
+        items=[],
+    )
+
+    buf = ["Y" * 80]
+    result = hud.process(buf, ctx)
+
+    second_line = result[1]
+    assert "80%" in second_line, f"Intensity 80% not found in: {second_line}"