docs: update documentation to reflect actual implementation status

Many features were documented as "missing" or "planned" but are actually
working: generics, string interpolation, File/HTTP/Random/Time effects,
JSON parsing, module system, and JIT CLI integration.

Updated IMPLEMENTATION_PLAN.md, OVERVIEW.md with accurate status.
Added ROADMAP.md (use-case-targeted) and LANGUAGE_COMPARISON.md.

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

docs/OVERVIEW.md

@@ -111,12 +111,51 @@ toString(42)        // "42"
 typeOf([1, 2, 3])   // "List"
 ```
 
-### Planned (Not Yet Implemented)
+### Also Working
 
-- **Schema Evolution**: Versioned types with automatic migrations
-- **Behavioral Types**: Properties like `is pure`, `is idempotent`
-- **Modules/Imports**: Code organization
-- **Compilation**: Currently interpreter-only
+```lux
+// Generic type parameters
+fn map<T, U>(f: fn(T): U, list: List<T>): List<U> = ...
+fn identity<T>(x: T): T = x
+
+// String interpolation
+let name = "Alice"
+Console.print("Hello, {name}!")  // Hello, Alice!
+Console.print("1 + 2 = {1 + 2}") // 1 + 2 = 3
+
+// File effects
+let content = File.read("config.txt")
+File.write("output.txt", "Hello!")
+let exists = File.exists("file.lux")
+
+// HTTP effects
+let response = Http.get("https://api.example.com/data")
+Http.post("https://api.example.com/submit", "{\"key\": \"value\"}")
+
+// Random effects
+let n = Random.int(1, 100)
+let coin = Random.bool()
+
+// Time effects
+let now = Time.now()
+Time.sleep(1000)  // milliseconds
+
+// JSON parsing
+let obj = Json.parse("{\"name\": \"Alice\"}")
+let str = Json.stringify(obj)
+
+// Module system
+import mymodule
+import utils/helpers as h
+import math.{sqrt, abs}
+import prelude.*
+```
+
+### Planned (Not Yet Fully Implemented)
+
+- **Schema Evolution**: Parsing works (`@v1`, `from @v1`), type system integration missing
+- **Behavioral Types**: Parsing works (`is pure`, `is total`), verification beyond `pure` missing
+- **Full Compilation**: JIT works for numeric code, strings/lists/ADTs missing
 
 ---
 
@@ -168,12 +207,10 @@ Quick iteration with type inference and a REPL.
 
 | Limitation | Description |
 |------------|-------------|
-| **Interpreter Only** | No compilation to native/JS/WASM yet |
-| **No Modules** | Can't split code across files |
-| **Limited IO** | Only Console built-in, no file/network |
-| **No Generics** | Polymorphic functions not fully implemented |
+| **Limited JIT** | Cranelift JIT works for numeric code only |
+| **No Package Manager** | Can't share/publish packages yet |
 | **New Paradigm** | Effects require learning new concepts |
-| **Small Ecosystem** | No packages, libraries, or community |
+| **Small Ecosystem** | No community packages yet |
 | **Early Stage** | Bugs likely, features incomplete |
 
 ---
@@ -232,10 +269,9 @@ Quick iteration with type inference and a REPL.
 
 ### Not a Good Fit (Yet)
 
-- Production applications (too early)
-- Performance-critical code (interpreter)
-- Large codebases (no modules)
-- Web development (no JS compilation)
+- Large production applications (early stage)
+- Performance-critical code (JIT limited to numeric)
+- Web frontend development (no JS compilation)
 - Systems programming (no low-level control)
 
 ---
@@ -282,20 +318,36 @@ Source Code
 │ Type Checker│  → Typed AST + Effect Tracking
 └─────────────┘
     │
-    ▼
-┌─────────────┐
-│ Interpreter │  → Values + Effect Handling
-└─────────────┘
+    ├─────────────────────────┐
+    ▼                         ▼
+┌─────────────┐       ┌──────────────┐
+│ Interpreter │       │ JIT Compiler │
+│ (default)   │       │ (Cranelift)  │
+└─────────────┘       └──────────────┘
+    │                         │
+    ▼                         ▼
+Values + Effects        Native Code
+                       (~160x speedup)
 ```
 
 ---
 
 ## Future Roadmap
 
-1. **Standard Library** - List, String, Option utilities
-2. **Module System** - Import/export, namespaces
-3. **JavaScript Backend** - Run in browsers
-4. **Schema Evolution** - Versioned types
-5. **Behavioral Types** - is pure, is idempotent
-6. **LSP Server** - IDE support
-7. **Package Manager** - Share code
+**Complete:**
+- ✅ Standard Library (List, String, Option, Result, JSON)
+- ✅ Module System (imports, exports, aliases)
+- ✅ LSP Server (basic diagnostics, hover, completions)
+- ✅ Generics and String Interpolation
+- ✅ File/HTTP/Random/Time Effects
+
+**In Progress:**
+1. **Behavioral Type Verification** - Total, idempotent, deterministic checking
+2. **Schema Evolution** - Type system integration, auto-migration
+3. **Error Message Quality** - Elm-style suggestions
+
+**Planned:**
+4. **HTTP Server Effect** - Build web APIs
+5. **SQL Effect** - Database access
+6. **Package Manager** - Share code
+7. **JavaScript Backend** - Run in browsers