fix: address 2 bugs from Devin Review on workspaceStore

[devin-ai-integration]

Summary

Fixes 2 bugs identified by Devin Review (PR #4) in src/stores/workspaceStore.ts:

1. updateChildrenPaths uses String.replace() which incorrectly matches substrings
   child.path.replace(oldPath, newPath) only replaces the first occurrence and can match mid-path substrings (e.g. renaming /src would corrupt /src2/file). Fixed by using startsWith() + slice() to only replace the path prefix.

2. duplicateFile doesn't deep-clone children when duplicating folders
   Spreading ...node copies the children array by reference, so duplicated folders share the same child objects with identical id and path values. Added a deepCloneFileNode helper that recursively creates new IDs and correct paths for all descendants.

Review & Testing Checklist for Human

• Rename a folder that has a sibling folder whose name starts with the same prefix (e.g. rename utils when utils-extra exists) — verify utils-extra children are unaffected
• Duplicate a folder with nested subfolders — verify all children have unique IDs and paths under the new copy
• Verify existing file tree operations (create, delete, move) still work correctly

Notes

Lint (npm run lint) and typecheck (tsc -b) both pass.

Link to Devin session: https://app.devin.ai/sessions/8da679d231384b9f8006427ea1372f8a
Requested by: @Huynhthuongg

[devin-ai-integration]

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[devin-ai-integration]

Devin Review found 2 potential issues.

[Huynhthuongg]

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[Huynhthuongg]

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[Huynhthuongg]