Implement static loadTriangle method to read triangle data from file

[avery-jingxin]

Description

We need to implement a static method loadTriangle(String path) in the NumberTriangle class that loads triangle data from a file.

Requirements

• Read triangle data from the specified file path
• Parse the file contents and create a NumberTriangle object
• Handle invalid file paths with appropriate error handling
• Support the expected file format for triangle data

Expected Behavior

The method should:

1. Take a file path as a String parameter
2. Read and parse the file contents
3. Return a properly initialized NumberTriangle object
4. Throw appropriate exceptions for invalid inputs or file errors

Acceptance Criteria

• Method signature matches specification
• File reading implemented correctly
• Error handling for invalid files
• Unit tests added and passing