[BUG] Claude Code Misunderstands NotebookEdit Insert Operation

## Environment

• Platform (select one):
• [x] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [ ] Other: <!-- specify -->
• Claude CLI version: v1.0.25
• Operating System: Ubuntu 22.04.5 LTS
• Terminal: Cursor (Integrated Terminal)

## Bug Description
Claude Code misunderstands the NotebookEdit tool's insert operation. When asked to insert a cell after a specific cell, it incorrectly uses that cell's index instead of the next index.

## Steps to Reproduce

1. Create a Jupyter notebook with cells containing: cell-0 (title), cell-1 (imports), cell-2 (code)
2. Ask Claude Code: "Insert a new cell after the imports cell"
3. Claude Code incorrectly uses cell_id="cell-1" thinking this means "after cell-1"
4. The new cell appears at position 1, pushing imports down to cell-2
5. Point out that the new cell is now before imports, not after
6. Claude Code repeats the same mistake when asked to fix it

## Expected Behavior
To insert after cell-1, Claude Code should use cell_id="cell-2" because:

• Insert operation places the new cell AT the specified index
• To place something after cell-1, it must go at position 2

## Actual Behavior
Claude Code:

• Uses cell_id="cell-1" when trying to insert after cell-1
• Places content before the target cell instead of after
• Continues making the same error despite corrections