Add DefaultMaxExpansionDepth constant and depth tracking in expandStep
to prevent runaway nested expansions. The limit applies to template
children during expansion.
Changes:
- Add DefaultMaxExpansionDepth = 5 constant
- Update expandStep to track depth and return error when exceeded
- Update ApplyExpansions callers to handle errors
- Add TestExpandStepDepthLimit test for depth limiting
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
84c124fc3d