Commit 1 Initial commit:
  Initial commit - MusicDriveSync

  MusicDriveSync is a wxPython desktop application for managing music on car
  thumb drives. The user maintains a large FLAC library on a NAS, organized as
  Artist/Album/Tracks. Rather than physically inserting drives to update them,
  each thumb drive has a corresponding folder on the NAS. The app lets the user
  browse the NAS library, see which tracks are already on a given drive
  (highlighted green), copy missing tracks to the drive folder, and remove
  tracks from it. Syncing to the physical drive is done separately via rsync.

  This initial commit includes a working application with the following:

  - config.py: reads and validates musicdrivesync.ini
  - MusicDriveSync_Lib.py: NAS library scanning with cache, drive folder
    scanning with progress callback, comparison index, copy and remove stubs
  - panels/LibraryPanel.py: wx.TreeCtrl-based library tree with green
    highlighting for tracks present on the active drive, Show Missing Only
    filter, and Copy Selected button
  - panels/DrivePanel.py: wx.TreeCtrl-based drive folder tree with Remove
    Selected button and confirmation dialog
  - main.py: top-level frame wiring drive selector, both panels, status bar
    progress during library and drive scans, path accessibility checks on startup

  ---
  Commit 2 Changelog and CLAUDE.md:
  Add changelog system, fix CLAUDE.md conflicts, and apply session bug fixes

  Introduces a changelog/ folder to track bugs, architectural decisions, and
  lessons learned across the life of the project.

  - changelog/CHANGELOG_INDEX.md: master index table for all entries
  - changelog/00001_arch.md: DataViewTreeCtrl to wx.TreeCtrl migration
  - changelog/00002_bug.md: missing drive scan progress feedback fix
  - changelog/00003_arch.md: library panel color logic reversal

  - CLAUDE.md: corrected two conflicts with the current codebase:
    color coding description updated (green = on drive, normal = needs copying);
    DataViewCtrl note replaced with TreeCtrl decision with pointer to changelog;
    UI layout diagram corrected; changelog folder added to project structure

  - panels/DrivePanel.py: converted from DataViewTreeCtrl to wx.TreeCtrl
  - MusicDriveSync_Lib.py: added progress_callback to ScanDriveFolder()
  - main.py: wired drive scan progress to status bar; added path accessibility
    checks at startup

  ---
  Commit 3 Fix Remove Selected:
  Fix Remove Selected, add safety guard, and document NAS read-only rule

  - Fixed "No tracks selected" on Remove and Copy buttons. Both panels were
    using TreeItemId.GetID() as a dict key which is unreliable across the wx
    layer. Replaced with wx.TreeCtrl's native SetItemData/GetItemData. The
    separate _item_data dict was removed from both panels entirely.
    See changelog/00004_bug.md.

  - Fixed 5-minute UI freeze after removing tracks. OnRemoveTracks was calling
    ScanDriveFolder() on the UI thread after every remove. Replaced with an
    in-memory filter of _drive_tracks using the list of removed relative paths.

  - Silent remove failures now surface as a warning dialog.

  - Added path prefix guard to RemoveTracksFromDrive(). Any file whose path
    does not begin with drive_path is unconditionally skipped.

  - Added Absolute Rules section to CLAUDE.md: the NAS music library is
    strictly read-only. The app may never delete or modify files there.

  - changelog/00004_bug.md: documents the SetItemData fix and lessons learned.

  ---
  Commit 4 Copy and Tools menu:
  Implement CopyTracksToDrive, add Tools menu with Empty Folder Report

  CopyTracksToDrive (MusicDriveSync_Lib.py):
  - Copies files preserving full folder structure relative to music_library_path
    (e.g. Compilations/Album/track.flac mirrors exactly on the drive folder)
  - Uses shutil.copy2 to preserve file timestamps and metadata
  - Skips files that already exist at the destination
  - Accepts a progress_callback(done, total) for status bar updates

  OnCopyTracks / _on_copy_complete (main.py):
  - Copy now runs in a background thread, no UI freeze for large selections
  - Status bar updates as each file is copied (e.g. "Copying to Taco... 3/12")
  - After completion, newly copied files are added to _drive_tracks in memory
    by reading their tags directly, no full rescan needed
  - Both panels disabled during copy and re-enabled on completion

  Tools menu (main.py):
  - Added Tools menu to the right of File in the menu bar
  - Empty Folder Report: scans the active drive folder and lists all
    subdirectories that contain no FLAC files (may still contain jpg/png etc.)
  - Results shown relative to drive root for readability
  - EmptyFolderReportDialog class added to main.py

  FindFoldersWithoutFlac (MusicDriveSync_Lib.py):
  - Two-pass walk: marks all dirs containing FLACs and their ancestors, then
    collects highest-level dirs with no FLACs using topdown pruning