Update prompt_plan.md to mark Task 5.2 as completed

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: ritwik-g

guide/prompt_plan.md

@@ -216,14 +216,15 @@ Organize commands:
 - Help texts for all commands
 ```
 
-#### Task 5.2: Error Handling
+#### Task 5.2: Error Handling ✅
 ```prompt
 Implement consistent errors:
 - Format: "Error: [context] - [specific issue]"
 - Validation: List all failures
 - Use rich formatting with fallback for non-TTY
 - Suggest solutions where possible
 ```
+**Status**: Completed - Centralized ErrorHandler with consistent formatting, stderr output, error aggregation, and solution suggestions across all commands
 
 ### Phase 6: Testing & Docs
 #### Task 6.1: Unit Tests ✅