feat(fiber): harden type safety, add scheduler + showcase

- Centralise all unsafe Lane/Lanes/Flags casts into src/fiber/bitwise.ts
- Implement binary min-heap scheduler (O(log n)) in src/fiber/minHeap.ts
- Wire concurrent rendering path (performConcurrentWorkOnRoot + renderRootConcurrent)
- Simplify branded types: Lanes = Lane alias, HookEffectTag = number
- Add 9 new test modules: bitwise, minHeap, typeGuards, lanes, scheduler,
  resumability, hydration, fiberUtils, commitIntegration
- Add compile-time type enforcement test (types.typecheck.ts)
- Export useMemo / useCallback / useReducer from index.ts
- Build interactive browser showcase (examples/interactive-showcase/)
- Update README: 473 tests, zero type errors, Phase 13 complete

Typecheck: 0 errors
Tests: 473 pass, 0 fail, 1,526 expects across 38 files

Author: MarcelOlsen

README.md

@@ -60,27 +60,28 @@ Each phase includes clear specifications, working implementations, and extensive
 
 ## Current Status
 
-🆕 **Current Phase**: Stable Release Track - Phase 12 ✅ **COMPLETE**
+🆕 **Current Phase**: Stable Release Track - Phase 13 ✅ **COMPLETE**
 
 **Latest Achievements**:
 
-- ✅ **Phase 12 Complete**: Performance Optimization Suite - memo, useMemo, useCallback with comprehensive test coverage
-- ✅ **Enhanced Performance**: React.memo equivalent for component memoization and optimization hooks
-- ✅ **272 Tests Passing**: Comprehensive test suite covering all functionality including performance optimizations
-- ✅ **Zero Linter Issues**: Clean codebase with consistent formatting and biome configuration
-- ✅ **Complete Performance Toolkit**: memo, useMemo, useCallback hooks for production-grade optimization
-- ✅ **Production-Ready**: Robust error handling, TypeScript support, and comprehensive edge case coverage
-- ✅ **Package Preparation**: Ready for npm registry publication with performance features
+- ✅ **Fiber Reconciler**: Real React-like fiber architecture with work loop, begin/complete work, and commit phases
+- ✅ **Lane-Based Priorities**: Branded `Lane`/`Lanes` type system with priority scheduling and lane merging
+- ✅ **Scheduler**: Binary min-heap task queue with `scheduleCallback`, `shouldYield`, and priority levels
+- ✅ **Concurrent Rendering Groundwork**: `performConcurrentWorkOnRoot` with time-slicing support
+- ✅ **Type Safety Hardening**: Centralised unsafe-cast boundary (`bitwise.ts`), zero stray `as number` casts, compile-time enforcement
+- ✅ **473 Tests Passing**: Comprehensive test suite across 38 files with 1,526 expectations
+- ✅ **Zero Type Errors**: `bun typecheck` clean (0 errors)
+- ✅ **Interactive Showcase**: Live browser demo at `examples/interactive-showcase/`
 
-**Stable Release Progress**: 1/9 phases complete (11% complete) 🚀
+**Stable Release Progress**: 2/9 phases complete (22% complete) 🚀
 
 **Immediate Milestones**:
 
-- 🚀 **npm Package Publication**: Package will be available on npm registry soon
-- 📦 **Alpha Release v0.1.0**: Complete core React-like functionality now available
-- 📚 **Documentation & Examples**: Comprehensive guides and demo applications
+- 🚀 **npm Package v0.3.0**: Published with fiber reconciler and performance toolkit
+- 📚 **Documentation & Examples**: Interactive showcase + updated API docs
+- 🧪 **Testing & Quality Assurance**: Phase 19 test coverage underway
 
-**Post-Alpha Roadmap**: 12 additional phases planned for stable v1.0.0 release with advanced features including concurrent rendering, SSR, dev tools, and production optimizations.
+**Post-Alpha Roadmap**: 11 additional phases planned for stable v1.0.0 release with advanced features including concurrent rendering, SSR, dev tools, and production optimizations.
 
 ---
 
@@ -378,7 +379,7 @@ const App = () => {
 
 ### 📋 Testing & Quality
 
-- **261 Comprehensive Tests**: Full test coverage for all features and edge cases including all hooks
+- **473 Comprehensive Tests**: Full test coverage for all features and edge cases including all hooks
 - **TypeScript Support**: Full type safety with detailed type definitions
 - **Linting & Formatting**: Biome-based code quality and consistent formatting
 - **Error Handling**: Graceful degradation and helpful error messages
@@ -581,7 +582,7 @@ mini-react/
 - ✅ Advanced rendering (Portals, Fragments)
 - ✅ Production-ready reconciliation engine
 - ✅ Comprehensive TypeScript support
-- ✅ 261 tests with full coverage
+- ✅ 473 tests with full coverage
 - ✅ Developer-friendly API matching React patterns
 - ✅ npm package ready for publication
 

examples/interactive-showcase/index.html

@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8" />
+  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+  <title>MiniReact — Interactive Showcase</title>
+  <link rel="stylesheet" href="style.css" />
+  <link rel="preconnect" href="https://fonts.googleapis.com" />
+  <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
+  <link href="https://fonts.googleapis.com/css2?family=DM+Mono:wght@300;400;500&family=DM+Serif+Display&family=Inter:wght@400;500;600&display=swap" rel="stylesheet" />
+</head>
+<body>
+  <div id="root"></div>
+  <div id="portal-target" class="portal-target" aria-label="Portal target"></div>
+  <script type="module" src="main.ts"></script>
+</body>
+</html>