Pattern algebra and the reactive contract

[l2hyunwoo]

Goal

Make compiled patterns first-class values (transform, combine, embed) and write down the reactive contract callers can rely on. Together these enable:

Jindong(speed) {
    Clip(heartbeat.timeStretch(1f / speed))
}

A state change reshapes the timeline; there is no imperative replay call anywhere.

Work items, in dependency order

• feat(core): add pattern algebra transforms on HapticPattern #88 pattern algebra transforms (core)
• feat(compose): add Clip node for embedding pattern values in the DSL #90 Clip node and core clip alias
• docs: formalize the reactive contract (trigger keys, frozen parameters, cancel-and-restart) #91 reactive contract docs and regression tests
• feat(sample): add algebra demo screen #92 sample algebra demo screen

Spun out along the way: #93 (execute/executeAsync overlap), #89 (keyless reactive patterns, post-R1).

Gate

Everything builds on the serial-timeline pipeline in #85, which merges first: reversed() and then can produce overlapping events, and #85 is what serializes overlaps at playback.

[l2hyunwoo]

All work items are implemented and open as a stack of PRs.

• feat(core): add pattern algebra transforms on HapticPattern #88 → feat(core): add pattern algebra transforms on HapticPattern #96 (base main)
  • feat(compose): add Clip node for embedding pattern values in the DSL #90 → feat(compose): add Clip node for embedding pattern values in the DSL #97 (base feat(core): add pattern algebra transforms on HapticPattern #96)
    • docs: formalize the reactive contract (trigger keys, frozen parameters, cancel-and-restart) #91 → docs: formalize the reactive contract (trigger keys, frozen parameters, cancel-and-restart) #98 (base feat(compose): add Clip node for embedding pattern values in the DSL #97)
    • feat(sample): add algebra demo screen #92 → feat(sample): add algebra demo screen #99 (base feat(compose): add Clip node for embedding pattern values in the DSL #97)
• executeAsync can leave an in-flight vibration untracked while execute is running #93 → fix(core): track in-flight execute() playback so executeAsync cancels it #95 (independent, base main)

Merge order: #95 any time; then #96 → #97 → (#98, #99), rebasing each base onto main as it merges. All gated on #85, which is already merged.