fix(desktop): allow FUSE rename on SMB backend

[FSM1]

Summary

• Simplify access() to always grant if the inode exists — POSIX permission checks add no security value in a single-user encrypted vault and break the FUSE-T SMB backend (proxied UID mismatch causes EACCES on access(W_OK), blocking rename)
• Unify UID/GID assignment in create() and mkdir() to use getuid()/getgid() instead of req.uid()/req.gid(), matching root inode and populate_folder() patterns
• Update desktop CLAUDE.md known limitations to reflect fix

Test plan

• echo "test" > ~/CipherBox/testfile.txt — create file
• mv ~/CipherBox/testfile.txt ~/CipherBox/renamed.txt — same-dir rename
• mkdir ~/CipherBox/sub && mv ~/CipherBox/renamed.txt ~/CipherBox/sub/ — cross-folder move
• Verified content integrity after each operation
• cargo check --features fuse — no new warnings

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Fixed rename operation failures on macOS with SMB backend
  • Improved access control handling for FUSE file operations

• Documentation

  • Added documentation for known limitation: Stale mount behavior after application crash and recommended recovery steps

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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Walkthrough

Planning documentation updated to mark a FUSE rename issue on SMB backend as fixed. FUSE operations code modified to derive UID/GID from process context instead of request context, and access permission checks changed to permissive validation. Desktop documentation updated to reflect the fix and document new known limitations.

Changes

Cohort / File(s)	Summary
Planning & Documentation .planning/STATE.md, apps/desktop/CLAUDE.md	Updated pending todos count from 6 to 5, removed completed FUSE rename fix item. Documented SMB rename issue as resolved; added "Stale mount after crash" as new known limitation.
FUSE Operations apps/desktop/src-tauri/src/fuse/operations.rs	Changed UID/GID derivation in file creation operations from request context to process context via libc::getuid()/libc::getgid(). Modified access permission checks from owner-based POSIX enforcement to permissive existence validation. Marked unused request parameters with underscore prefix.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: fixing FUSE rename functionality on the SMB backend by simplifying access checks and unifying UID/GID assignment.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/fuse-rename-smb

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