fix: improve error message clarity in workflow handling

[akarsh1010]

Fixes #2

What this PR does

Adds workflow/handler.py with descriptive error messages that replace
generic errors (e.g., "error") with context-rich messages that tell
developers exactly what failed and why.

Changes

• Created workflow/handler.py with WorkflowError custom exception
• load_workflow(): descriptive errors for missing path, file not found,
  permission denied, and empty file
• validate_workflow(): descriptive errors for missing 'steps', wrong type,
  and missing 'name'/'action' fields per step
• execute_step(): descriptive errors for non-callable actions and runtime failures
• run_workflow(): orchestrates validation and execution with full error context

Before / After

Before	After
raise Exception("error")	raise WorkflowError("Workflow loading failed: 'file_path' must not be empty...")

[akarsh1010]

Hi! I've submitted PR #3 to fix this issue. I created workflow/handler.py with descriptive error messages replacing all generic ones. Each error now tells the developer exactly what failed, why, and how to fix it. Would love your feedback!