Fidelity pass: tighten forward-lunge, drop two ill-fitting prop moves

Checked the FK-approximation movements by sampling real bone world positions:
- forward-lunge: feet differed ~13cm in height (front foot clipped the floor
  after grounding). Re-tuned angles so the feet land level (Δy ~2cm) with a clear
  0.32m stride and upright torso.
- single-leg-calf-raise: kept (acceptable "foot points, body holds" approximation,
  same as relevé).
- step-up & triceps-dips: REMOVED. Both need a front-facing box, but our only
  box/bench prop (the chair) is placed behind the figure for sit-back moves, so the
  lead foot / hands landed in empty space. Deferred to a future front-box prop
  (noted in docs/coverage-gap.md) rather than ship a low-fidelity render.

135 tests pass; build green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018WCktDrKYZpJjCb2apbqWp

Author: claude

docs/coverage-gap.md

@@ -41,16 +41,21 @@ Ordered by gap size × how cleanly the engine renders it:
 
 1. **Core** — `plank-hold`, `mountain-climber` (plank pose), `crunch`,
    `bicycle-crunch`, `supine-leg-raise` (supine pose). Highest-value, cleanest.
-2. **Chest** — register the existing `push-up`, add `wall-pushup` (wall prop).
+2. **Chest** — register the existing `push-up`.
 3. **Back** — `superman` (prone pose).
-4. **Upper legs** — `forward-lunge`, `step-up` (chair prop).
-5. **Upper arms** — `triceps-dips` (chair/bar prop).
-6. **Lower legs** — `single-leg-calf-raise`.
-7. **Conditioning / mobility** — `jumping-jacks`, `standing-quad-stretch`
+4. **Upper legs** — `forward-lunge` (FK split stance, feet leveled).
+5. **Lower legs** — `single-leg-calf-raise`.
+6. **Conditioning / mobility** — `jumping-jacks`, `standing-quad-stretch`
    (single-leg + reach-IK).
 
-These 13–14 movements roughly **double our chest/core/back coverage** and close the
-most glaring holes — all on today's engine, no new primitives required.
+These ~10 movements roughly **double our chest/core/back coverage** — all on
+today's engine, no new primitives required.
+
+**Deferred (need a front-facing prop we don't have):** `step-up` and
+`triceps-dips`. Our only box/bench prop (the chair) is placed *behind* the figure
+for sit-back moves, so a step-up's lead foot and a dip's hands land in empty space.
+These return once we add a front-placed box / dip-station prop (and anchor-aware
+ground-lock) — a clean roadmap item rather than a forced, low-fidelity render.
 
 ## Metadata gap (drives the catalogue work)
 

playground/src/presets.ts

@@ -80,9 +80,7 @@ import bicycleCrunch from "../../spec/examples/bicycle-crunch.movit?raw";
 import supineLegRaise from "../../spec/examples/supine-leg-raise.movit?raw";
 import superman from "../../spec/examples/superman.movit?raw";
 import forwardLunge from "../../spec/examples/forward-lunge.movit?raw";
-import stepUp from "../../spec/examples/step-up.movit?raw";
 import calfRaise from "../../spec/examples/single-leg-calf-raise.movit?raw";
-import tricepsDips from "../../spec/examples/triceps-dips.movit?raw";
 import jumpingJacks from "../../spec/examples/jumping-jacks.movit?raw";
 import quadStretch from "../../spec/examples/standing-quad-stretch.movit?raw";
 
@@ -124,9 +122,7 @@ export const PRESETS: Preset[] = [
   { id: "supine-leg-raise", label: "Lying leg raise", domain: "Fitness", bodyPart: "Core", target: "Abdominals", equipment: "Body weight", difficulty: "Beginner", source: supineLegRaise },
   { id: "superman", label: "Superman", domain: "Fitness", bodyPart: "Back", target: "Spinal erectors", equipment: "Body weight", difficulty: "Beginner", source: superman },
   { id: "forward-lunge", label: "Forward lunge", domain: "Fitness", bodyPart: "Upper legs", target: "Quadriceps", equipment: "Body weight", difficulty: "Intermediate", source: forwardLunge },
-  { id: "step-up", label: "Step-up (box)", domain: "Functional", bodyPart: "Upper legs", target: "Quadriceps", equipment: "Chair", difficulty: "Beginner", source: stepUp },
   { id: "calf-raise", label: "Single-leg calf raise", domain: "Fitness", bodyPart: "Lower legs", target: "Calves", equipment: "Body weight", difficulty: "Intermediate", source: calfRaise },
-  { id: "triceps-dips", label: "Triceps dips (box)", domain: "Fitness", bodyPart: "Upper arms", target: "Triceps", equipment: "Chair", difficulty: "Intermediate", source: tricepsDips },
   { id: "jumping-jacks", label: "Jumping jacks", domain: "Warm-up", bodyPart: "Full body", target: "Full body", equipment: "Body weight", difficulty: "Beginner", source: jumpingJacks },
   { id: "quad-stretch", label: "Standing quad stretch", domain: "Mobility", bodyPart: "Upper legs", target: "Quadriceps", equipment: "Body weight", difficulty: "Beginner", source: quadStretch },
 

spec/examples/forward-lunge.movit

@@ -3,11 +3,11 @@ movit exercise "Forward lunge"
   pose start = standing
 
   step "Lunge" 1.6s ease-in-out:
-    hip_right: flex 50
-    knee_right: flex 85
-    hip_left: extend 18
-    knee_left: flex 80
-    ankle_right: dorsiflex 12
+    hip_right: flex 45
+    knee_right: flex 95
+    hip_left: extend 15
+    knee_left: flex 45
+    ankle_right: dorsiflex 14
     spine: extend 4
     ground-lock: feet
     cue "Step forward and lower the back knee toward the floor"