refactor: remove NewDefaultFileConfigProvider function

- Remove NewDefaultFileConfigProvider() from file/provider.go
- Update documentation to reflect single constructor pattern
- Replace factory method examples with explicit NewFileConfigProvider(configFile) usage
- Update architecture docs to emphasize --config flag support over factory methods
- Simplify API by having only one constructor for FileConfigProvider

This simplifies the API surface and makes config file handling more explicit.
The --config flag implementation now provides all the functionality that the
factory method was intended to provide, but with better user control and
transparency.

Author: orien

docs/architecture/configuration.md

@@ -330,24 +330,25 @@ stacks:
 The file provider offers two creation methods to support different architectural needs:
 
 ```go
-// Method 1: Explicit filename (for custom config files)
-provider := file.NewFileConfigProvider("custom-config.yaml")
+// Create file provider with explicit filename
+provider := file.NewFileConfigProvider("stackaroo.yaml")
 
-// Method 2: Default factory (recommended - no hardcoded filenames)
-provider := file.NewDefaultFileConfigProvider()  // Uses "stackaroo.yaml"
+// Or with custom config file
+provider := file.NewFileConfigProvider("custom-config.yaml")
 ```
 
-**Architectural Benefits of `NewDefaultFileConfigProvider()`:**
-- **Encapsulates filename knowledge** - Consumer modules don't need to know config filename
-- **Consistent defaults** - All applications use same config file name
-- **Easy configuration** - Single source of truth for default behavior
+**Architectural Benefits:**
+- **Explicit configuration** - Clear specification of config file location
+- **Flexible configuration** - Support for custom config file names via --config flag
+- **Consistent interface** - Single constructor pattern for all use cases
 - **Testable** - Mock providers can use different factory implementations
 
 ### **Loading Configuration**
 
 ```go
-// Create file provider with default config file
-provider := file.NewDefaultFileConfigProvider()
+// Create file provider with specified config file
+configFile := "stackaroo.yaml"  // From --config flag or default
+provider := file.NewFileConfigProvider(configFile)
 
 // Load configuration for specific context
 cfg, err := provider.LoadConfig(ctx, "prod")
@@ -357,8 +358,6 @@ if err != nil {
 
 // Access resolved configuration
 fmt.Printf("Deploying to account: %s\n", cfg.Context.Account)
-fmt.Printf("Region: %s\n", cfg.Context.Region)
-fmt.Printf("Stacks: %d\n", len(cfg.Stacks))
 ```
 
 ### **Individual Stack Access**

docs/architecture/resolver.md

@@ -202,7 +202,8 @@ flowchart LR
 
 ```go
 // Example usage in deploy command
-configProvider := file.NewDefaultFileConfigProvider()  // No hardcoded filename
+configFile := "stackaroo.yaml"  // From --config flag or default
+configProvider := file.NewFileConfigProvider(configFile)
 templateReader := &resolve.FileTemplateReader{}
 resolver := resolve.NewStackResolver(configProvider, templateReader)
 
@@ -244,11 +245,11 @@ graph TD
 
 #### **cmd/deploy Module**
 - **Pure CLI orchestration** - No file system knowledge
-- **Uses factory methods** - `file.NewDefaultFileConfigProvider()` instead of hardcoded filenames
+- **Uses explicit config files** - `file.NewFileConfigProvider(configFile)` with --config flag support
 - **Dependency injection** - Accepts resolver and configuration provider interfaces
 
 #### **config/file Module**  
-- **Owns "stackaroo.yaml" filename** - Via `NewDefaultFileConfigProvider()` factory
+- **Handles config file resolution** - Via --config flag with "stackaroo.yaml" default
 - **Path-to-URI conversion** - Converts relative paths to `file://` URIs
 - **Configuration file knowledge** - Understands YAML structure and resolution
 

internal/config/file/provider.go

@@ -28,11 +28,6 @@ func NewFileConfigProvider(filename string) *FileConfigProvider {
 	}
 }
 
-// NewDefaultFileConfigProvider creates a new file-based ConfigProvider using the default config filename
-func NewDefaultFileConfigProvider() *FileConfigProvider {
-	return NewFileConfigProvider("stackaroo.yaml")
-}
-
 // LoadConfig loads and resolves configuration for the specified context
 func (fp *FileConfigProvider) LoadConfig(ctx context.Context, context string) (*config.Config, error) {
 	// Load raw config if not already loaded