Stage 1: project setup, Exercise Library, both Mode designs and the Mode switch

- Flutter Android app on CookIT's stack (provider, shared_preferences, gen-l10n)
- tools/exercise-import turns free-exercise-db into 876 bundled Exercises
  with 1,746 WebP images (20 MB); stretching -> Stretching, rest -> Workout
- ZenStyle tokens per Mode: calm rounded sage/teal with breath ripples vs.
  dark ember-to-red with floor-tape slashes; the theme morphs at each
  Mode's own pace
- Remembered global Mode switch, Plans / Library / History tabs

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/exercise-import/tests/test_exercise_import.py

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+import json
+
+from PIL import Image
+
+from exercise_import import mode_of, run, slim
+
+RAW = {
+    "id": "Calf_Stretch",
+    "name": "Calf Stretch",
+    "force": "static",
+    "level": "beginner",
+    "mechanic": None,
+    "equipment": "body only",
+    "primaryMuscles": ["calves"],
+    "secondaryMuscles": [],
+    "instructions": ["Stand tall. ", "", "Lean forward."],
+    "category": "stretching",
+    "images": ["Calf_Stretch/0.jpg", "Calf_Stretch/1.jpg"],
+}
+
+
+def test_stretching_category_is_stretching_mode_and_others_workout():
+    assert mode_of("stretching") == "stretching"
+    for category in ["strength", "plyometrics", "cardio", "powerlifting"]:
+        assert mode_of(category) == "workout"
+
+
+def test_slim_keeps_needed_fields_and_cleans_instructions():
+    result = slim(RAW)
+    assert result["mode"] == "stretching"
+    assert result["instructions"] == ["Stand tall.", "Lean forward."]
+    assert result["imageCount"] == 2
+    assert "images" not in result
+
+
+def test_run_writes_json_and_flattened_small_webps(tmp_path):
+    source = tmp_path / "db"
+    (source / "dist").mkdir(parents=True)
+    (source / "exercises" / "Calf_Stretch").mkdir(parents=True)
+    (source / "dist" / "exercises.json").write_text(json.dumps([RAW]), encoding="utf-8")
+    for i in range(2):
+        Image.new("RGB", (850, 567), "white").save(source / "exercises" / "Calf_Stretch" / f"{i}.jpg")
+
+    out = tmp_path / "out"
+    run(source, out)
+
+    written = json.loads((out / "exercises.json").read_text(encoding="utf-8"))
+    assert [e["id"] for e in written] == ["Calf_Stretch"]
+    with Image.open(out / "images" / "Calf_Stretch_1.webp") as image:
+        assert max(image.size) == 480