Add local dir parameter

[BBC-Esq]

This PR adds a new local_dir parameter to provide more flexible control over model downloads.

A lot of people like to actually see the native files and work with them that way rather than HF's weird "cache" structure and naming.

Key Changes

• Added local_dir parameter to both load() and download_models() methods
• When specified, downloads preserve repository structure in the target directory
• Added precedence handling: local_dir takes priority over other download location parameters

Usage Example

# Download to specific directory, maintaining repo structure
chat.load(source="huggingface", local_dir="path/to/dir")

# Download to specific directory with local source
chat.load(source="local", local_dir="path/to/dir")

Download Configuration Guide

The source parameter along with cache_dir and local_dir control how and where model files are downloaded:

Source: "huggingface"

Downloads directly from the Hugging Face repository:

Parameters	Behavior	Repo Structure?
(default)	Downloads to ~/.cache/huggingface using HF's cache system	No
cache_dir="path"	Downloads to specified path using HF's cache system	No
local_dir="path"	Downloads to specified path preserving repository structure	Yes

Source: "local"

Downloads from GitHub releases instead of Hugging Face:

Parameters	Behavior	Repo Structure?
(default)	Downloads to current directory	No
cache_dir="path"	Downloads to specified path	No
local_dir="path"	Downloads to specified path preserving repository structure	Yes

Source: "custom"

Uses existing files from a specified path:

Parameters	Behavior	Repo Structure?
custom_path	Uses existing files at the specified path	n/a
+cache_dir	cache_dir parameter is ignored	n/a
+local_dir	local_dir parameter is ignored	n/a

Repository Structure

When "Repo Structure?" is:

• Yes: Files are downloaded maintaining the original repository's directory structure
• No: Files are downloaded using a flattened or cache-specific structure
• n/a: Uses files exactly as they exist in the custom path

Parameter Precedence and Usage Examples

• Parameter precedence (highest to lowest):
• local_dir (if specified, takes precedence over all other parameters)
• cache_dir (used if local_dir is not specified)
• Default location (used if neither local_dir nor cache_dir specified):
  • ~/.cache/huggingface (when source="huggingface")
  • Current directory (when source="local")

[fumiama]

You can use custom_path for all those functions and add some enum or bool params to indicate its function in order to reduce the complexity.