Implement BetterFit iOS strength training coach core framework

[Copilot]

Swift Package Manager framework implementing an iOS/watchOS strength training coach with auto-tracking, AI adaptation, and social features.

Architecture

Models (6 files)

• Exercise, Workout, WorkoutTemplate - Core workout data structures
• TrainingPlan with TrainingGoal enum (strength, hypertrophy, endurance, powerlifting, general fitness, weight loss)
• BodyMapRecovery - Time-based recovery tracking across 7 body regions with 4 states
• UserProfile, Challenge, Streak - Social features with 4 challenge goal types

Services (3 files)

• AutoTrackingService - Watch accelerometer/gyroscope rep detection via motion magnitude thresholds
• AIAdaptationService - Analyzes completion rate, progressive overload, plateau detection
• EquipmentImageService - 3D/AI equipment image library with async generation support

Features (7 managers)

• PlanManager - Multi-week training plan management
• TemplateManager - Template CRUD, tag/name search, recent templates
• EquipmentSwapManager - Alternative exercise suggestions based on available equipment
• BodyMapManager - Recovery recommendations, overall recovery percentage
• SocialManager - Streak tracking, challenge leaderboards
• SmartNotificationManager - Optimal workout time detection, overtraining alerts

Usage

let betterFit = BetterFit()

// Create workout from template with equipment swaps
var workout = betterFit.templateManager.createWorkout(from: templateId)!
let swaps = betterFit.equipmentSwapManager.suggestSwaps(for: workout)
if let alt = swaps.first?.alternatives.first {
    betterFit.equipmentSwapManager.applySwap(
        workout: &workout,
        originalExerciseId: swaps.first!.original.id,
        newExercise: alt
    )
}

// Auto-track with Watch sensors
betterFit.startWorkout(workout)
let event = betterFit.processMotionData(
    MotionData(acceleration: [x, y, z], rotation: [rx, ry, rz])
)

// Complete workout (updates recovery, streak, AI analysis)
betterFit.completeWorkout(workout)

Recovery System Behavior

When multiple muscle groups map to the same body region (e.g., quads + glutes → legs), recovery status compounds per workout: recovered → fatigued → sore. This prevents over-training specific regions.

Test Coverage

30 tests across models, services, features, and integration flows. Swift Package Manager project targeting iOS 17+, watchOS 10+.

Original prompt

BetterFit is an open-source strength training coach for iOS and Apple Watch. It auto-tracks sets and reps via Watch sensors, adapts plans with AI, and uses clean consistent 3D/AI equipment images. Core features: plan mode, reusable workout templates, fast swaps for available equipment, body-map recovery view, social streaks and challenges, and smart notifications that minimise gym admin time.

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.