Module loader 

Template loading with override support.

Responsibilities:

• Load templates from .ralph/templates/{name}.json first.
• Fall back to built-in templates if no custom template exists.
• List all available templates (built-in + custom).
• Validate templates and return warnings for unknown variables.

Not handled here:

• Template content validation beyond JSON parsing.
• Template merging with user options (see merge.rs).

Invariants/assumptions:

• Custom templates override built-ins with the same name.
• Template files must have .json extension.
• Template names are case-sensitive.
• Variable validation is performed (unknowns produce warnings; strict mode fails).

Structs

LoadedTemplate

Result of loading a template with context

TemplateInfo

Metadata for a template (used for listing)

Enums

TemplateError

Error type for template operations

TemplateSource

Source of a loaded template

Functions

get_template_context

Get the template context for inspection

list_templates

List all available templates (built-in + custom)

load_template

Load a template by name

load_template_with_context

Load a template by name with variable substitution

load_template_with_context_legacy

Load a template by name with variable substitution (legacy, non-strict)

template_exists

Check if a template exists (either custom or built-in)