feat: Enhance #use directive for directories and cwd

The `#use` directive now supports referencing entire directories,
automatically including all `.myc` files within them. Additionally,
environments are now initialized with the current working directory as a
default search path, simplifying module resolution.

docs/dependency_management.md

@@ -20,20 +20,21 @@ We need a way to explicitly define dependencies *within* a Myc script, ensuring
 
 ## The Solution: `#use` Preprocessor Directives
 
-We introduce a preprocessor directive `#use` that is evaluated *before* the main parsing phase begins.
+We introduce a preprocessor directive `#use` that is evaluated *before* the main parsing phase begins. It can target either single files or entire directories.
 
 ### Syntax
 
 ```myc
 #use math->indicators
 #use utils
+#use mylib
 
 (do
   ;; Actual Myc code begins here
   (def my_var (indicators.calculate ...))
 )
 ```
-*(Here `math->indicators` resolves to `math/indicators.myc` and `utils` resolves to `utils.myc`)*
+*(Here `math->indicators` resolves to the file `math/indicators.myc`. `utils` resolves to `utils.myc`. If `mylib` is a directory instead of a file, it resolves to all `.myc` files within that directory.)*
 
 ### Implementation Plan
 
@@ -41,13 +42,15 @@ We introduce a preprocessor directive `#use` that is evaluated *before* the main
    The `Environment` will be extended with a `HashSet<PathBuf>` (e.g., `loaded_modules`) to keep track of canonical paths that have already been loaded, ensuring idempotency.
 
 2. **Pre-Parse Extraction:**
-   Before the AST `Parser` processes a script, a lightweight scraper will read the top lines of the file. It will extract all `#use` paths and stop as soon as it encounters a line that is not empty, not a comment (`;`), and not a `#use` directive.
+   Before the AST `Parser` processes a script, a lightweight scraper will read the top lines of the file. It will extract all `#use` paths and stop as soon as it encounters a line that is not empty, not a comment (`;` or `#`), and not a `#use` directive.
 
 3. **Recursive Resolution:**
-   - The scraper extracts the module path, replaces `->` with the OS-specific directory separator, and appends `.myc`.
-   - Paths are resolved relative to the file that declares the dependency.
+   - The scraper extracts the module path and replaces `->` with the OS-specific directory separator.
+   - It first checks if `<path>.myc` exists as a file. If it does, it resolves to that single file.
+   - If not, it checks if `<path>` is a directory. If so, it resolves to all `.myc` files inside that directory (sorted alphabetically).
+   - Paths are resolved relative to the file that declares the dependency, with a fallback to the global `--lib` search paths.
    - If a path is not in `loaded_modules`, it is added to the set.
-   - The file is read, and the extraction process runs recursively on its content.
+   - The files are read, and the extraction process runs recursively on their content.
    - This creates a flat list of all dependencies in a valid topological order.
 
 4. **Two-Pass Compilation:**