019fd304 anatomy - #6

- New i18n module (app/lib/i18n.tsx): language store via useSyncExternalStore
  (hydration-safe, persists choice in localStorage, defaults to browser
  language), 88 UI strings per language, fmt() template helper.
- New app/lib/anatomy-ru.ts: full Russian translations for all 9 organs —
  descriptions, key facts, conditions, hotspot labels — plus genitive-case
  forms so Russian templates stay grammatically correct.
- Language switcher (EN/RU) in the topbar; viewer hotspots, search, quiz,
  modals and 3D canvas aria-label all switch without reloading the model
  (viewer.updateHotspots).
- Fix two factual issues flagged in REVIEW.md: pancreas classified as
  Digestive & Endocrine, intestine length clarifies small vs large intestine.

Co-authored-by: arena-agent <297053741+arena-agent@users.noreply.github.com>

The single-page app needs no Context.Provider; components subscribe to the
module-level store via useSyncExternalStore directly. This removes the React
19 dev warning about multiple renderers sharing a context provider during
vinext HMR updates and keeps hydration-safe SSR (getServerSnapshot = en).

Co-authored-by: arena-agent <297053741+arena-agent@users.noreply.github.com>

…on, sources

- Real quiz engine: 45 bilingual questions (5 per organ) with immediate
  feedback, educational explanations, live score and retry flow
  (app/lib/content/questions.ts, QuizFlow).
- Body systems view: 12 systems with bilingual descriptions and organ
  membership; Systems nav button now works; preselects the current
  organ's system (app/lib/content/systems.ts, SystemsView).
- Structured lessons: learning objectives, structure, function, clinical
  perspective and bibliography per organ, EN and RU (app/lib/content/lessons.ts,
  LessonContent). Russian lessons add Sinelnikov/Sapin references.
- Full comparison modal: 6-row property table between the organ and its
  reference counterpart (CompareTable).
- Medical disclaimer footer and 'educational, not medical advice' note in
  lessons.
- Search now covers descriptions, tissues, conditions and hotspot labels.
- Content integrity tests (tests/content-data.test.mjs): 20 checks covering
  quiz validity, system coverage and lesson completeness.

Co-authored-by: arena-agent <297053741+arena-agent@users.noreply.github.com>

…view

- Real function animations in the 3D viewer, procedural and bilingual:
  heart lub-dub cycle, lung breathing, peristalsis, eye scanning, organ
  pulses and glandular bobs. 'Animate' now animates the actual model in
  the viewer with a labelled chip (play + stop) instead of a static modal
  (app/lib/content/animations.ts, viewer.setFunctionAnimation).
- Labelled histology per organ in every lesson: tissue layers with
  one-line descriptions, EN and RU (app/lib/content/histology.ts).
- Quiz results now include an answer review: every missed question with
  your answer vs the correct one.
- Content tests extended to 38 checks (histology parity, animation
  labels/descriptions).

Co-authored-by: arena-agent <297053741+arena-agent@users.noreply.github.com>

- 21 new organs across all 12 systems: stomach, gallbladder, esophagus,
  tongue, spleen, thymus, lymph node, thyroid, adrenals, pituitary,
  trachea, larynx, bladder, uterus, ovary, testis, prostate, spinal cord,
  diaphragm, biceps, femur.
- scripts/generate-organs.mjs: procedural GLB models (Three.js +
  GLTFExporter, 20-150 KB each) fitted to the same normalized space as the
  original assets; hotspot coordinates are auto-snapped onto the model
  surface so the 3D dots land on the correct features.
- Full bilingual content for each new organ: EN/RU data, systems
  membership, 3-question quiz bank (63 questions), structured lessons,
  3-layer histology, function animations; search covers all of it.
- tsconfig: allowImportingTsExtensions so Node-based content tests can
  import TS modules directly.
- Content tests now run 124 checks across 30 organs, RU parity, systems
  coverage, lessons, histology and animations.

Co-authored-by: arena-agent <297053741+arena-agent@users.noreply.github.com>

- Progress store (app/lib/progress.ts): visited organs, lesson views,
  animation plays, quiz results (best/attempts), saved organs and per-organ
  notes — persisted in localStorage, hydration-safe via useSyncExternalStore.
- Profile modal: statistics (organs explored, quizzes taken, lessons viewed,
  animations played), average best quiz score, per-organ progress bars with
  lesson/animation/saved icons, saved organs chips, notes list, clear-progress
  action. Library/Notes nav buttons and the profile button now open it.
- Notes modal: per-organ notes with auto-save and quick switching between
  organs that have notes.
- Organ library: bookmark button saves the current organ; 'Saved' filter
  shows the collection; saved organs carry a bookmark dot.
- Medical imaging: per-organ modality + clinical note (EN/RU) in every
  lesson; 12 schematic imaging illustrations (X-ray/CT/MRI/ultrasound style,
  webp + 2 svg) in public/imaging, always labeled as schematic educational
  images, never real clinical scans.
- Tests extended to 156 checks (imaging parity + file existence, progress
  store logic).

Co-authored-by: arena-agent <297053741+arena-agent@users.noreply.github.com>

- New route /systems (app/systems/page.tsx + SystemsPage): full-page
  overview of the twelve body systems.
- BodyFigure: stylised SVG human figure with all 30 modelled organs as
  clickable shapes; selecting a system highlights its organs and dims the
  rest; 12-colour system palette shared with the legend; keyboard
  accessible (Enter/Space).
- Left panel: system list with colour dots and organ counts. Right panel:
  system description and organ chips that deep-link to the organ on the
  home page. Footer note on how the systems work together.
- Home page now accepts deep links: /?organ=<id> selects an organ and
  /?modal=lesson|profile|notes opens a modal (server-driven via searchParams
  + remount key — no client-only state sync needed).
- Header navigation becomes links on the systems page; home 'Systems'
  button links to /systems; the old in-modal SystemsView is removed.
- BodyFigure exports SYSTEM_COLORS; organ groups carry id=organ-<id>.

Co-authored-by: arena-agent <297053741+arena-agent@users.noreply.github.com>