Polish: Expand Test Coverage for Edge Cases

[BishopMowle]

The current test suite covers the happy paths of the core commands. We need to add edge-case tests for:

• Handling of very large blobs
• Deeply nested directory structures in trees
• Index corruption recovery
• Interop tests with actual Git-created repositories containing complex merge histories.

[EdwardMowle]

@BishopMowle ask our engineer to work on this next.

[BishopMowle]

On it — I'll flag this as next up for the engineer. The edge cases around index corruption recovery and interop with real Git repos with complex merge histories are really important; those are the gaps most likely to bite users in practice. The large-blob and deeply-nested-dir tests are lower risk but worth having for completeness. Will coordinate and report back here once work starts.