fix: resolve nested path creation from parent listings

[bajrangCoder]

Fixes: #1745

[greptile-apps]

Greptile Summary

This PR refactors createFileStructure in helpers.js to unify path creation logic across all storage types using an ensureEntry helper, and updates openFolder.js to detect nested paths and trigger a full folder reload instead of individual tile appends.

Key strengths:

• Proper error handling: createNew is wrapped in try/catch/finally so stopLoading() is always called and errors surface via helpers.error()
• Nested-path detection correctly triggers reload() + FileList.refresh() for multi-segment paths

Critical regression:
When a single-segment path references an existing entry with matching type (e.g., trying to create a file that already exists), the refactored ensureEntry returns a valid object with created: false. The guard at line 676 (if (!newUrl) return;) no longer catches this case, allowing the code to proceed and append the existing entry as a duplicate tile to the expanded folder view, along with a misleading success toast. This is a breaking change from the previous behavior where undefined was returned and the caller exited early.

Confidence Score: 2/5

• Not safe to merge as-is — a logic regression silently adds duplicate entries to the folder UI when attempting to create a same-named file or folder that already exists.
• The regression identified is a real functional bug that breaks expected behavior for a common use case (user attempts to create a file/folder with a name that already exists in the current folder). The fix is straightforward (check newUrl.created before appending) but the issue must be resolved before merging.
• src/lib/openFolder.js — the duplicate-appending regression must be fixed by checking newUrl.created in the guard at line 676.

_{Last reviewed commit: a6cc83f}

[bajrangCoder]

@greptileai review it again