feat: Std::String, Std::Map, Result/Option, ? operator, sizeof fix, docs

Add standard library modules:
- Std::String: strlen, strcmp, concat, copy, starts_with wrappers
- Std::Map: linear-probing hash map with String keys, int values

Add error handling:
- Result and Option algebraic enum examples
- ? try operator for automatic error propagation in HIR lowering

Compiler bugfixes:
- Fix sizeof() for user-defined structs (new hSizeOf HIR node)
- Fix HIR type lowering for char8, bool8, int8, uint8, etc.
- Fix let statement lowering for pointer types (*char8 → int* bug)
- Fix PrintInt ABI mismatch (int64_t → int in io.c)
- Fix Makefile test bug (_test_tmp_pkg already exists)

Documentation:
- Rewrite README.md with features, examples, project structure
- Add docs/LanguageRef.md — complete language reference
- Add docs/Stdlib.md — standard library documentation
- Add docs/BuildAndTest.md — build and test guide

New examples: strings, map, result_option, try_operator (13 total)

README.md

@@ -4,6 +4,10 @@
 
 Bux is a fast, compiled, strongly-typed systems programming language inspired by [Rux](https://rux-lang.dev/). The long-term goal is a self-hosted compiler with a minimal runtime, native x86-64 backend, and modern tooling.
 
+Bux improves on Rux with a richer standard library (`Map`, `String`), modern error handling (`Result`, `Option`, and the `?` operator), and a portable C transpiler backend that runs on Linux, macOS, and Windows.
+
+---
+
 ## Quick Start
 
 ```bash
@@ -12,26 +16,156 @@ make build
 
 # Create a new project
 bux new hello
+cd hello
 
 # Build and run
 bux run
 ```
 
+---
+
 ## Syntax Preview
 
+### Hello World
 ```bux
 import Std::Io::PrintLine;
 
 func Main() -> int {
-    let message: *char8 = c8"Hello, Bux!";
-    PrintLine(message);
+    PrintLine("Hello, Bux!");
     return 0;
 }
 ```
 
-## Roadmap
+### Error Handling with `?`
+```bux
+enum Result {
+    Ok(int),
+    Err(String)
+}
 
-See [`PLAN.md`](PLAN.md) for the full roadmap to self-hosting.
+func Divide(a: int, b: int) -> Result {
+    if b == 0 {
+        return Result_NewErr("division by zero");
+    }
+    return Result_NewOk(a / b);
+}
+
+func Compute() -> Result {
+    let x: int = Divide(10, 2)?;  // auto-propagates Err
+    let y: int = Divide(x, 5)?;
+    return Result_NewOk(y);
+}
+```
+
+### Structs and Methods
+```bux
+struct Rectangle {
+    width: int;
+    height: int;
+}
+
+extend Rectangle {
+    func Area(self: Rectangle) -> int {
+        return self.width * self.height;
+    }
+}
+
+func Main() -> int {
+    let rect: Rectangle = Rectangle { width: 10, height: 5 };
+    PrintInt(rect.Area());
+    return 0;
+}
+```
+
+### Generics
+```bux
+func Max<T>(a: T, b: T) -> T {
+    if a > b {
+        return a;
+    }
+    return b;
+}
+
+func Main() -> int {
+    let m: int = Max<int>(10, 20);
+    PrintInt(m);
+    return 0;
+}
+```
+
+### Hash Map
+```bux
+import Std::Map::{Map, Map_New, Map_Set, Map_Get};
+
+func Main() -> int {
+    let m: Map = Map_New(16);
+    Map_Set(&m, "answer", 42);
+    PrintInt(Map_Get(&m, "answer"));
+    return 0;
+}
+```
+
+---
+
+## Features
+
+| Feature | Status |
+|---------|--------|
+| **Types** | Primitives, pointers, slices, tuples, structs, enums, unions |
+| **Generics** | Generic functions (monomorphization) |
+| **Algebraic Enums** | Enums with data (`Result`, `Option`) |
+| **Pattern Matching** | `match` with guards |
+| **Methods** | `extend` blocks for struct methods |
+| **Interfaces** | `interface` + `extend` for trait-like behavior |
+| **Error Handling** | `Result<T,E>`, `Option<T>`, and the `?` operator |
+| **Standard Library** | `Io`, `Array`, `String`, `Map` |
+| **Backend** | C transpiler (bootstrap) |
+| **Tooling** | `bux new`, `bux build`, `bux run`, `bux check` |
+
+---
+
+## Project Structure
+
+```
+bux/
+├── src/              # Bootstrap compiler (Nim)
+├── stdlib/           # Standard library (.bux + .c runtime)
+├── examples/         # Example programs
+├── tests/            # Unit tests (Nim)
+├── docs/             # Documentation
+├── README.md
+├── PLAN.md           # Roadmap to self-hosting
+└── Makefile
+```
+
+---
+
+## Build & Test
+
+```bash
+# Build compiler
+make build
+
+# Run all tests
+make test
+
+# Run example programs
+make test-examples
+
+# Clean build artifacts
+make clean
+```
+
+---
+
+## Documentation
+
+- [`docs/LanguageRef.md`](docs/LanguageRef.md) — Language reference
+- [`docs/Stdlib.md`](docs/Stdlib.md) — Standard library documentation
+- [`docs/BuildAndTest.md`](docs/BuildAndTest.md) — Build and test guide
+- [`PLAN.md`](PLAN.md) — Roadmap to self-hosting
+
+---
 
 ## License