feat: custom mode user-controlled weight/reps (PRD #51 US2)

[tomkis]

Summary

• Add changeReps domain method + event + API mutation for custom mode reps input
• Custom mode adjust overlay: two NumericalInput fields (weight + reps) instead of slider
• Skip exercise assessment prompt in custom mode (null assessment stored)
• Skip lifestyle feedback modal in custom mode
• Exercise replacement mid-workout starts blank (null weight/reps) in custom mode
• Thread progressionMode from mesocycle to workout UI via enriched getWorkout return type

Closes PRD #51 User Story 2: "As a user who prefers manual control, I want to enter my own weight/reps each workout so that the app doesn't override my programming decisions."

Test plan

• pnpm typecheck — 0 errors
• pnpm lint — 0 errors (6 pre-existing warnings)
• pnpm knip — clean
• pnpm test — 332/332 passing
• Manual: custom mode → open adjust overlay → weight + reps inputs shown (no slider)
• Manual: custom mode → finish exercise → no assessment modal
• Manual: custom mode → finish last exercise → no lifestyle feedback modal
• Manual: custom mode → replace exercise → new exercise has blank sets

Findings

• exerciseAssesment on FinishedWorkingExercise is now nullable — downstream getProgressionType guards for null but custom mode never reaches extendMicrocycle (throws)
• progressionMode is NOT on workoutSchema (causes issues in internal workout construction); instead enriched at the getWorkout API boundary
• ExerciseRepsChanged event only updates pending sets (done/failed sets keep their reps)

🤖 Generated with Claude Code