fix: C backend String functions, record type aliases, docs cleanup

- Add String.fromChar, chars, substring, toUpper, toLower, replace,
  startsWith, endsWith, join to C backend
- Fix record type alias unification by adding expand_type_alias and
  unify_with_env functions
- Update docs to reflect current implementation status
- Clean up outdated roadmap items and fix inconsistencies
- Add comprehensive language comparison document

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/COMPILATION_STRATEGY.md

@@ -9,8 +9,10 @@ Lux should compile to native code with zero-cost effects AND compile to JavaScri
 | Component | Status |
 |-----------|--------|
 | Interpreter | Full-featured, all language constructs |
+| C Backend | Complete (functions, closures, pattern matching, lists, RC) |
+| JS Backend | Complete (full language, browser & Node.js, DOM, TEA) |
 | JIT (Cranelift) | Integer arithmetic only, ~160x speedup |
-| Targets | Native (via Cranelift JIT) |
+| Targets | Native (via C), JavaScript, JIT |
 
 ## Target Architecture
 
@@ -296,45 +298,33 @@ Tree increment(Tree tree) {
 
 ## Milestones
 
-### v0.2.0 - C Backend (Basic)
-- [ ] Integer/bool expressions → C
-- [ ] Functions → C functions
-- [ ] If/else → C conditionals
-- [ ] Let bindings → C variables
-- [ ] Basic main() generation
-- [ ] Build with GCC/Clang
+### C Backend - COMPLETE
+- [x] Integer/bool expressions → C
+- [x] Functions → C functions
+- [x] If/else → C conditionals
+- [x] Let bindings → C variables
+- [x] Basic main() generation
+- [x] Build with GCC/Clang
+- [x] Strings → C strings
+- [x] Pattern matching → Switch/if chains
+- [x] Lists → Linked structures
+- [x] Closures
+- [x] Reference counting (lists, boxed values)
 
-### v0.3.0 - C Backend (Full)
-- [ ] Strings → C strings
-- [ ] Records → C structs
-- [ ] ADTs → Tagged unions
-- [ ] Pattern matching → Switch/if chains
-- [ ] Lists → Linked structures
-- [ ] Effect compilation (basic)
+### JavaScript Backend - COMPLETE
+- [x] Basic expressions → JS
+- [x] Functions → JS functions
+- [x] Effects → Direct DOM/API calls
+- [x] Standard library (String, List, Option, Result, Math, JSON)
+- [x] DOM effect (40+ operations)
+- [x] Html module (type-safe HTML)
+- [x] TEA runtime (Elm Architecture)
+- [x] Browser & Node.js support
 
-### v0.4.0 - Evidence Passing
-- [ ] Effect analysis
-- [ ] Evidence vector generation
-- [ ] Transform effect ops to direct calls
-- [ ] Handler compilation
-
-### v0.5.0 - JavaScript Backend
-- [ ] Basic expressions → JS
-- [ ] Functions → JS functions
-- [ ] Effects → Direct DOM/API calls
-- [ ] No runtime bundle
-
-### v0.6.0 - Reactive Frontend
-- [ ] Reactive primitives
-- [ ] Fine-grained DOM updates
-- [ ] Compile-time dependency tracking
-- [ ] Svelte-like output
-
-### v0.7.0 - Memory Optimization
-- [ ] Reference counting insertion
-- [ ] Reuse analysis
-- [ ] FBIP detection
-- [ ] In-place updates
+### Remaining Work
+- [ ] Evidence passing for zero-cost effects
+- [ ] FBIP (Functional But In-Place) optimization
+- [ ] WASM backend (deprioritized)
 
 ## References