docs: update status for completed JS backend and package manager

- JS_WASM_BACKEND_PLAN: Mark phases 1-5 complete, deprioritize WASM
- LANGUAGE_COMPARISON: Update package manager status
- OVERVIEW: Add completed features list
- ROADMAP: Mark JS backend and package manager complete
- Add PACKAGES.md documenting the package system

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

docs/PACKAGES.md

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+# Lux Package System
+
+Lux includes a built-in package manager for managing dependencies.
+
+## Quick Start
+
+### Initialize a Project
+
+```bash
+# Create a new project directory
+lux init my-project
+cd my-project
+
+# Or initialize in an existing directory
+lux pkg init
+lux pkg init my-project-name
+```
+
+This creates a `lux.toml` manifest file:
+
+```toml
+[project]
+name = "my-project"
+version = "0.1.0"
+description = "A Lux project"
+
+[dependencies]
+# Add dependencies here
+```
+
+### Adding Dependencies
+
+```bash
+# From a git repository
+lux pkg add mylib --git https://github.com/user/mylib
+
+# From a local path
+lux pkg add local-lib --path ../lib
+
+# With a specific version (for future registry support)
+lux pkg add http 1.0.0
+```
+
+### Installing Dependencies
+
+```bash
+lux pkg install
+```
+
+This installs all dependencies listed in `lux.toml` to the `.lux_packages/` directory.
+
+### Using Packages
+
+Once installed, import packages in your Lux code:
+
+```lux
+import mylib
+
+let result = mylib.doSomething()
+```
+
+## Commands Reference
+
+| Command | Description |
+|---------|-------------|
+| `lux pkg init [name]` | Initialize a lux.toml in the current directory |
+| `lux pkg install` | Install all dependencies from lux.toml |
+| `lux pkg add <pkg>` | Add a dependency |
+| `lux pkg remove <pkg>` | Remove a dependency |
+| `lux pkg list` | List dependencies and their status |
+| `lux pkg update` | Update all dependencies |
+| `lux pkg clean` | Remove installed packages |
+
+## Dependency Sources
+
+### Git Repository
+
+```toml
+[dependencies]
+mylib = { git = "https://github.com/user/mylib" }
+mylib = { git = "https://github.com/user/mylib", branch = "main" }
+```
+
+### Local Path
+
+```toml
+[dependencies]
+local-lib = { path = "../local-lib" }
+```
+
+### Registry (Future)
+
+```toml
+[dependencies]
+http = "1.0.0"
+```
+
+## Package Structure
+
+A valid Lux package must have one of these entry points:
+
+1. `lib.lux` - Main module file in package root
+2. `src/lib.lux` - Main module file in src directory
+
+Example package structure:
+
+```
+mypackage/
+├── lux.toml
+├── lib.lux          # Entry point (option 1)
+└── src/
+    └── lib.lux      # Entry point (option 2)
+```
+
+The entry point should export public functions:
+
+```lux
+// lib.lux
+pub fn helper(x: Int): Int = x * 2
+
+pub fn process(data: String): String = {
+    // Implementation
+    data
+}
+```
+
+## Project Layout
+
+A typical Lux project looks like:
+
+```
+my-project/
+├── lux.toml           # Project manifest
+├── src/
+│   └── main.lux       # Main source file
+├── tests/
+│   └── test.lux       # Test files
+└── .lux_packages/     # Installed dependencies (gitignore this)
+    ├── mylib/
+    │   └── lib.lux
+    └── utils/
+        └── lib.lux
+```
+
+## Standard Library
+
+The Lux standard library is available as a package:
+
+```bash
+lux pkg add stdlib --path /path/to/lux/stdlib
+```
+
+Or use the built-in modules directly:
+
+```lux
+// Built-in modules (always available)
+import html       // Type-safe HTML construction
+import browser    // Browser effects (Dom, Storage, Navigation)
+```
+
+## Best Practices
+
+1. **Add `.lux_packages/` to `.gitignore`** - Dependencies should be installed, not committed
+
+2. **Use semantic versioning** - When publishing packages, follow semver
+
+3. **Document your exports** - Add comments to public functions
+
+4. **Keep packages focused** - One package should do one thing well
+
+## Future Features
+
+- **Package Registry** - Central repository for sharing packages
+- **Version Resolution** - Automatic dependency version management
+- **Lock File** - Reproducible builds with exact versions
+- **Publishing** - `lux pkg publish` command