0.3.0-dev.1: AHAP accuracy fixes, primitives, AHAP parsing, demo app improvements

[imedboumalek]

Summary

• Fix a real AHAP bug: curve control point times are now encoded relative to the curve's start (Core Haptics spec), not absolute pattern time — every curve segment after the first in a long sound was previously mistimed on iOS
• Scale the intensity-curve point budget with segment duration (--curve-rate) so long/complex uploads keep envelope detail instead of being flattened into a fixed 32-point cap; RDP simplifier now binary-searches its tolerance to use the full budget
• Sample Android waveform amplitudes at step midpoints instead of segment starts, removing a half-step lag that dulled ramps
• Add Android primitive composition support: pattern.toPrimitives() + --formats primitives CLI output, mapping patterns onto VibrationEffect.Composition primitives
• Add AHAP parsing: HapticPattern.fromAhap + CLI accepts .ahap inputs directly, converting to Android formats without re-analyzing audio
• Fix the demo app's playback sync (vibration leading audio, playhead jump/reset) by driving the playhead from a monotonic clock keyed off PlayerState.playing instead of the player's position stream
• Fix demo app asset bundling after the CLI's new grouped output layout (assets/haptics/ahap/, assets/haptics/waveform/)
• Refactor the demo app's main.dart into models/, playback/, widgets/ — extracting a standalone PlaybackController

Version bumped to 0.3.0-dev.1 (prerelease); tag v0.3.0-dev.1 staged locally, not yet pushed.

Test plan

• dart analyze --fatal-infos clean on the package
• dart test — 139 tests passing (AHAP encoder/decoder, waveform, primitives, analyzer, CLI, MP3)
• flutter analyze clean on example_app
• flutter test passing on example_app
• dart pub publish --dry-run clean
• Manual on-device check of the demo app's playback sync fix (recommended before tagging/publishing)