Add the library-coverage handoff plan

Claude-Session: https://claude.ai/code/session_01HJDQQDA9QdP8zByg43H5v3

Exercise Library/TODO-coverage.md

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+# Handoff: right-size the exercise library by functional coverage
+
+Repo: `~/Documents/indie/Workouts`. Read `Exercise Library/SYSTEM.md` first
+(motion format, props, visual language), then one machine motion
+(`Leg Press/motion.json`) and one bodyweight motion (`Bird Dog/motion.json`)
+as templates, one `info.md` (`Leg Press/info.md`) plus its parser
+(`Workouts/ExerciseFigure/ExerciseInfo.swift` — it parses a fixed shape, not
+general Markdown), and `render.py` (`--sheet`, `--strict`, `--orbit`,
+`--export`, `--fixtures`).
+
+## The question this session answers
+
+Not "how many exercises" but "which movement patterns can a user not log?"
+The picker (`ExercisePickerView`) lists exactly the bundled library names and
+there is no free-text fallback — the library is the app's **closed catalog**.
+A missing pattern is a hard wall, not a cosmetic gap. Build the coverage
+model, audit against it, then author the gap-fillers in priority order.
+
+## The coverage model (starting point — refine it, don't rubber-stamp it)
+
+A movement-pattern × modality matrix. Patterns: squat, hinge, lunge,
+horizontal push, vertical push, horizontal pull, vertical pull, elbow
+flexion, elbow extension, shoulder raise (lateral/rear), hip ab/adduction,
+calf, core anti-extension, core rotation, core lateral, core flexion,
+mobility/warm-up. Modalities: machine, free weight (barbell/dumbbell),
+bodyweight/floor. A cell needs an exercise only if real programs train that
+pattern that way — the test for "done" is that a typical gym-goer (machine
+circuit, free-weight lifter, or home/bodyweight) can build their whole
+program from the picker. Write the filled matrix into SYSTEM.md (or a
+COVERAGE.md beside it) so future additions are judged the same way.
+
+## What a rough audit already shows (verify, then prioritize)
+
+- **Hinge: zero coverage in any modality** — no Deadlift, Romanian Deadlift,
+  Glute Bridge, or Hip Thrust. The single biggest hole; glutes are basically
+  untrained by the current catalog.
+- **No lunge pattern** (Lunge / Split Squat).
+- **Bodyweight column missing its canon**: Squat, Push-Up, Pull-Up.
+- **Free-weight column completely empty** — zero barbell/dumbbell exercises.
+  The `dumbbell` prop type exists in both renderers but has never been used
+  by a motion; its first real use may shake out bugs.
+- **Shoulder raise**: no Lateral Raise (machine Shoulder Press only).
+- **Core flexion**: no plain Crunch (machine Abdominal only).
+- Memory notes a desired "morning wake-up" mobility set (Cat-Cow exists;
+  neck rolls, arm circles, etc.) — decide whether it's this session or the
+  next phase.
+
+Filling these modestly lands around 40–46 total (currently 22) — "double the
+library" is the outcome, but the matrix decides which ones and in what order:
+hinge first, then lunge + bodyweight canon, then free weights, then
+isolation/mobility.
+
+## Authoring workflow, per exercise
+
+- New folder `<Name>/` with `motion.json` + `info.md`. The folder/`name`
+  string is user-facing (picker + run screen) — match the existing naming
+  register.
+- Pose keyframes in anatomical angles per SYSTEM.md; run
+  `python3 render.py --strict "<Name>"` (ROM violations are data bugs; a few
+  legacy warnings exist in old motions, add none), eyeball `preview.gif` AND
+  `orbit.gif` — every exercise orbits in-app now, so check ±45°/90°/180°,
+  not just the authored view.
+- Machines need props: scene slabs carry `z`/`depth` (see SYSTEM.md props
+  section), `bar`/`pad`/`roller`/`cable` ride joints. Free weights are
+  usually just a `bar` (with `plateR`) or `dumbbell` at the hands.
+- `info.md` must follow the parsed shape: `# Title`, summary paragraph,
+  the `**Category:** / **Type:** / **Targets:** / **Prescription:**` bullets,
+  then `## Setup / Execution / Cues / Common Mistakes / Progression`.
+  **Machine exercises' `Type:` must start "Machine-based"** — that prefix is
+  what shows the machine-settings UI (`ExerciseInfo.isMachineBased`).
+
+## Invariants — do not break
+
+- **Data-only expansion.** New exercises need zero Swift changes; if you find
+  yourself touching the schema or solver, stop and re-read SYSTEM.md — and
+  any schema change must land in `render.py`/`kinematics.py` and the Swift
+  port in lockstep, fixtures regenerated.
+- `WorkoutsTests/ExerciseMotionTests.swift` asserts
+  `fixtures.exercises.count == 22` — bump it to the new count and regenerate
+  with `python3 render.py --fixtures`. `allBundledMotionsBuildTimelines`
+  covers new motions automatically.
+- Starter splits and their fixed-ULID seeds are frozen — adding library
+  exercises must not touch `StarterSplits/` or `Workouts/Seed/`.
+- Every exercise ships both files: a motion with no `info.md` renders a blank
+  reference page in Settings → Library.
+
+## Verification workflow
+
+`python3 render.py --strict` (whole library) + `--sheet` and eyeball;
+`--orbit` for each new machine; `python3 render.py --export` then
+`python3 render.py --fixtures`; `xcodebuild test -scheme Workouts
+-destination 'platform=iOS Simulator,name=iPhone 17 Pro'
+-only-testing:WorkoutsTests` (48 green today; count assertion updated);
+`xcodebuild build -scheme "Workouts Watch App" -destination
+'generic/platform=watchOS Simulator'`. If test results ever contradict the
+source, suspect a stale incremental build — nuke DerivedData and rerun.
+One end-user CHANGELOG.md sentence per the app-changelog skill (e.g. the
+library doubles with deadlifts, lunges, push-ups, dumbbells…), README
+key-features line if it names library scope. Commit in reviewable batches
+(the coverage model + audit first, then exercises by pattern group), push,
+delete this file in the final commit.
+
+## Judgment calls you're empowered to make
+
+The final matrix rows and which cells count as "required"; the exact
+exercise picks per gap and their names; whether the mobility/"morning
+wake-up" set is in scope or explicitly deferred to the next phase; per-
+exercise camera yaw and prop minimalism (schematic silhouettes, never scale
+models).