fix(android): play impulse-only presets on hardware without primitive support

[piaskowyk]

What

Impulse-only presets — the percussive ones built from just discrete signals (Castanets, Stomp, Gavel, FingerDrum, HoofBeat, WarDrum… ~45 presets where the continuous amplitude is empty) — were silent on weaker/older Android hardware, while firing fine on capable phones and on web.

Why

These presets play via VibrationEffect.Composition primitives (addPrimitive(PRIMITIVE_TICK/CLICK…)), gated on areAllPrimitivesSupported() and API ≥ 30. Weaker/older actuators report no primitive support, so ImpulseCompositionHapticBuilder.createCompositionEffect() returns null and execution falls through to the continuous-envelope path (PeakLineBuilder + ControlLineBuilder.getStepsPoints @ 13 Hz). That path destroys transients:

• A single impulse at t=0 becomes a ~2 ms waveform — the step loop starts at currentTime=0 and discards the peak's negative-time pre-ramp, and the peak is only ~14 ms wide (2 ms at full amplitude) to begin with.
• On amplitude-control devices the energy is averaged across ~76 ms buckets down to ~7–27/255 — below a weak motor's start threshold.

So the motor never spins up (silent), or on timing-only devices the rhythm smears into one long buzz. A 2 ms pulse does fire on a fast LRA (Pixel-class), which is why it works on better phones — and web works because navigator.vibrate is binary on/off at full power (no amplitude dilution).

Fix

Add a crisp-waveform fallback scoped to impulse-only presets, tried right after the primitive path returns null (in HapticBuilder.createVibrationEffect):

• ImpulseCompositionHapticBuilder.createWaveformEffect / buildImpulseWaveform render each impulse as a 20 ms, (near-)full-power pulse via createWaveform, amplitude floored at 64/255, preserving inter-impulse gaps — mirroring the web Vibration API behavior that's confirmed working on the same hardware.
• Capable devices (primitive support) and mixed discrete+continuous presets (Poke, Snap, Blip) are untouched.

Tests

New JVM unit tests for the pure buildImpulseWaveform builder (Pulsar/src/test/.../ImpulseCompositionHapticBuilderTest.kt) — 4 tests, all passing; library compiles.

Reviewer notes

• Perceptual verification needs a physical weak device — it can't be felt on an emulator. The logic and code path are verified statically + via unit tests.
• Related, not addressed here: the realtime discrete path uses VibrationEffect.createOneShot(10, …) (10 ms) in RealtimePrimitiveComposer / RealtimeEnvelopeWithDiscretePrimitivesComposer, which likely has the same too-short-for-weak-hardware issue. Left out to keep this change scoped to preset playback.

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