feat: add bilateral left/right arm tracking for bicep curls

[Shikhar-404exe]

Summary #43

Adds independent left and right arm tracking for bicep curls. Previously the engine picked the "best visible side" and tracked only that arm. Now both arms are tracked independently — each arm counts reps when it completes a full curl cycle, and total reps = left + right.

Changes

Angle Computation (3 files)

• angleUtils.ts — Compute elbowLeft, elbowRight, shoulderLeft, shoulderRight from MediaPipe landmarks
• poseWorker.ts — Same bilateral angles in the web worker
• gpuAngleUtils.ts — Expand WGSL shader from 9→11 floats, add GPU-side elbowLeft/elbowRight

Config

• exercises.ts — Add bilateral?: boolean and bilateralJoints?: { left, right } to ExerciseConfig. Set bilateral: true on bicepCurl.

Engine

• exerciseEngine.ts — Core change:
  • EngineState gains 10 new optional fields: leftHistory, rightHistory, leftStage, rightStage, leftDownAngleReached, rightDownAngleReached, leftStageStartTime, rightStageStartTime, leftRepCount, rightRepCount
  • process() detects config.bilateral and runs two independent state machines (one per arm)
  • Each arm transitions up→down→up with its own smoothed angle, history buffer, cooldown, and down-duration tracking
  • reps = leftRepCount + rightRepCount
  • Undefined stages auto-initialize from current angle after calibration
  • Fix: removed duplicate properties in the return object (pre-existing)

Feedback

• feedbackEngine.ts — BicepCurl rules check leftStage/rightStage and shoulderLeft/shoulderRight instead of single-side only

Tests (3 new)

Test	Validates
Left-arm-only rep	Left arm completes curl while right stays extended; only leftRepCount increments
Bilateral simultaneous reps	Both arms complete curl in same frame; reps = 2
Fresh initialization	leftStage/rightStage initialize from angle when undefined

Verification

• 161/161 tests pass (12 test files)

Files Changed

src/config/exercises.ts                      
src/engine/feedbackEngine.ts                 
src/services/__tests__/exerciseEngine.test.ts 
src/services/angleUtils.ts                   
src/services/exerciseEngine.ts                
src/services/gpuAngleUtils.ts                
src/workers/poseWorker.ts                     

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[Somil450]

@Shikhar-404exe Thank you for the contribution.

This introduces a significant change to the rep-counting logic by moving from single-arm tracking to independent left/right arm tracking. Before I proceed further, could you please provide a short demo video showing:

• Left-arm-only curls counting correctly
• Right-arm-only curls counting correctly
• Simultaneous bilateral curls counting as two reps
• Existing bicep curl functionality continuing to work as expected

Also, please resolve the current merge conflicts with the latest main branch so the changes can be reviewed and tested properly.

[Shikhar-404exe]

https://drive.google.com/file/d/1zWE4mBk6PXwTGbvIP2VZ0xMIqmTTTKdA/view?usp=sharing demo video

[Shikhar-404exe]

any update on when this'll be merged ? i have linked the demo video of running this feature locally in my earlier comment.