docs: add comprehensive language documentation

Documentation structure inspired by Rust Book, Elm Guide, and others:

Guide (10 chapters):
- Introduction and setup
- Basic types (Int, String, Bool, List, Option, Result)
- Functions (closures, higher-order, composition)
- Data types (ADTs, pattern matching, records)
- Effects (the core innovation)
- Handlers (patterns and techniques)
- Modules (imports, exports, organization)
- Error handling (Fail, Option, Result)
- Standard library reference
- Advanced topics (traits, generics, optimization)

Reference:
- Complete syntax reference

Tutorials:
- Calculator (parsing, evaluation, REPL)
- Dependency injection (testing with effects)
- Project ideas (16 projects by difficulty)

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

docs/tutorials/README.md

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+# Tutorials
+
+Learn Lux by building real projects.
+
+## Standard Programs
+
+These tutorials cover common programming tasks:
+
+| Tutorial | What You'll Build | Concepts |
+|----------|-------------------|----------|
+| [Calculator](calculator.md) | REPL calculator | Parsing, evaluation, REPL loop |
+| [Todo App](todo.md) | CLI task manager | File I/O, data structures |
+| [HTTP Client](http-client.md) | API consumer | HTTP effects, JSON parsing |
+| [Word Counter](word-counter.md) | Text analyzer | File reading, string ops |
+
+## Effect Showcases
+
+These tutorials demonstrate Lux's unique effect system:
+
+| Tutorial | What You'll Learn | Key Concept |
+|----------|-------------------|-------------|
+| [Dependency Injection](dependency-injection.md) | Testing with mock handlers | Handler swapping |
+| [State Machines](state-machines.md) | Modeling state transitions | Custom effects |
+| [Effects Cookbook](effects-cookbook.md) | Common effect patterns | Handler patterns |
+
+## Quick Start: Your First Project
+
+### 1. Create Project Directory
+
+```bash
+mkdir my-first-lux
+cd my-first-lux
+```
+
+### 2. Create Main File
+
+```lux
+// main.lux
+
+fn main(): Unit with {Console} = {
+    Console.print("Welcome to my Lux project!")
+    Console.print("Enter your name:")
+    let name = Console.readLine()
+    Console.print("Hello, " + name + "!")
+}
+
+let output = run main() with {}
+```
+
+### 3. Run It
+
+```bash
+lux main.lux
+```
+
+### 4. Add a Module
+
+```lux
+// lib/greetings.lux
+
+pub fn hello(name: String): String =
+    "Hello, " + name + "!"
+
+pub fn goodbye(name: String): String =
+    "Goodbye, " + name + "!"
+```
+
+```lux
+// main.lux
+import lib/greetings as greet
+
+fn main(): Unit with {Console} = {
+    Console.print("Enter your name:")
+    let name = Console.readLine()
+    Console.print(greet.hello(name))
+    Console.print(greet.goodbye(name))
+}
+
+let output = run main() with {}
+```
+
+## Project Ideas by Difficulty
+
+### Beginner
+
+- **Temperature converter** - Convert between Celsius, Fahrenheit, Kelvin
+- **Number guessing game** - Random number with hints
+- **Simple quiz** - Multiple choice questions with scoring
+- **Unit converter** - Length, weight, volume conversions
+
+### Intermediate
+
+- **Markdown previewer** - Parse basic Markdown to HTML
+- **Contact book** - CRUD with file persistence
+- **Simple grep** - Search files for patterns
+- **CSV processor** - Read, filter, transform CSV files
+
+### Advanced
+
+- **Test framework** - Use effects for test isolation
+- **Config loader** - Effect-based configuration with validation
+- **Mini interpreter** - Build a small language
+- **Chat client** - HTTP-based chat application
+
+### Effect Showcases
+
+- **Transaction system** - Rollback on failure
+- **Capability security** - Effects as capabilities
+- **Async simulation** - Model async with effects
+- **Dependency graph** - Track and inject dependencies
+
+## How to Use These Tutorials
+
+1. **Read through first** - Understand the goal
+2. **Type the code** - Don't copy-paste
+3. **Experiment** - Modify and see what happens
+4. **Build your own** - Apply concepts to your ideas
+
+## Getting Help
+
+- Check the [Language Reference](../reference/syntax.md)
+- See [examples/](../../examples/) for working code
+- Use the REPL to experiment
+
+Happy building!