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>

README.md

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+# ZenXercise
+
+An offline Android app for stretching and working out. It has two fully separate Modes, Stretching
+and Workout. You build your own Plans from a bundled library of 876 exercises and follow them in a
+guided Player.
+
+- Domain terms: [GLOSSARY.md](GLOSSARY.md)
+- Decisions: [docs/adr/](docs/adr/)
+- Deferred ideas: [future_ideas.md](future_ideas.md)
+
+## Development
+
+```sh
+flutter pub get
+flutter test
+flutter run
+```
+
+The Exercise Library in `assets/exercises/` is generated from free-exercise-db by
+[tools/exercise-import](tools/exercise-import/README.md).