[Test] Verify source format consistency (string vs array)

[coderabbitai]

Context

From PR #34 review discussion: #34

The integration test normalizes all cell sources to strings for comparison, which could mask format inconsistencies where some cells have source as a string and others as an array.

Problem

• Resolved conflict cells use: source: resolvedContent.split(/(?<=\n)/) (always array)
• Identical cells use: cellToUse = currentCell || incomingCell || baseCell (keeps original format)
• Test's getCellSource() normalizes both, hiding potential issues

Impact

Low priority - doesn't affect core functionality but could cause issues with some notebook tools that expect consistent formatting.

Suggested Enhancement

Add a check after writing the notebook to verify all cells use the same source format (all strings or all arrays).

Backlinks:

• PR [FEAT] Create a Testing Harness #34: [FEAT] Create a Testing Harness #34
• Requested by: @Avni2000