feat(03-02): implement animation library — 7 types with registry and factory

- AnimationBase ABC with render(t, led_count) and from_params() contract
- SolidColorAnimation: time-independent uniform fill
- ChaseAnimation: moving lit segment with forward/reverse support
- PulseAnimation: sine-wave breathing effect (speed maps to period)
- RainbowAnimation: HSV hue cycle across strip via colorsys.hsv_to_rgb
- StrobeAnimation: on/off flashing at 1-20 Hz with configurable duty cycle
- ColorWipeAnimation: progressive fill from start or end
- FireAnimation: Fire2012 algorithm with cooling/sparking/heat-to-color mapping
- ANIMATION_REGISTRY + create_animation() factory function
- All 24 tests passing

lightsync/animations/strobe.py

@@ -0,0 +1,42 @@
+"""Strobe animation — rapid on/off flashing."""
+from lightsync.animations.base import AnimationBase
+
+
+class StrobeAnimation(AnimationBase):
+    """Rapid on/off flashing at configurable frequency and duty cycle.
+
+    speed=0.5 -> ~10.5 Hz. duty_cycle=0.1 means 10% on, 90% off.
+    """
+
+    def __init__(
+        self,
+        color: tuple[int, int, int] = (255, 255, 255),
+        speed: float = 0.5,
+        duty_cycle: float = 0.1,
+        white: int = 0,
+    ) -> None:
+        self.color = tuple(color)  # type: ignore[arg-type]
+        self.speed = speed
+        self.duty_cycle = duty_cycle
+        self.white = white
+
+    def render(self, t: float, led_count: int) -> list[tuple]:
+        # Frequency: 1-20 Hz mapped from speed 0.0-1.0
+        freq = 1.0 + self.speed * 19.0
+        phase = (t * freq) % 1.0
+
+        if phase < self.duty_cycle:
+            pixel = self.color
+        else:
+            pixel = (0, 0, 0)
+
+        return [pixel] * led_count
+
+    @classmethod
+    def from_params(cls, params: dict) -> "StrobeAnimation":
+        return cls(
+            color=tuple(params.get("color", [255, 255, 255])),  # type: ignore[arg-type]
+            speed=params.get("speed", 0.5),
+            duty_cycle=params.get("duty_cycle", 0.1),
+            white=params.get("white", 0),
+        )