Bug Fixes

• Single window enforcement - clicking the toolbar icon when the tracker window is already open now focuses the existing window instead of spawning a duplicate.
• Removed localStorage migration - startup no longer reads from localStorage, eliminating a code path that could silently overwrite data in browser.storage.local on open.

Enhancements
Main Window
- Auto-scroll after Generate - after generating episode groups, the right panel automatically scrolls to the targeted folder section so the new groups are immediately visible.
- Source-page row colouring - request log rows are now tinted with a rotating palette of 10 colours based on the page they originated from. Rows sharing the same source page share the same colour, making it easy to visually group related requests.
- Export Markdown downloads a file - the Export Markdown button now triggers a .md file download (named mediatracker-YYYY-MM-DD_HH-MM.md) instead of copying to the clipboard.

Quick Exclude (new)
- A ⊘ Exclude button has been added to the request detail pane header.
- Clicking it opens a mini dialog showing the URL's filename as individual character boxes.
- Clicking any character box selects that character through to the end of the filename as the exclusion suffix.
- Pressing Save appends the chosen suffix to the exclusion list and saves immediately — no need to open Preferences.

Preferences Dialog
- Export JSON downloads a file - the Export JSON button now downloads a mediatracker-YYYY-MM-DD.json file instead of copying to the clipboard.
- Import JSON picks a file - the Import JSON button now opens an OS file picker (.json) instead of showing a paste textarea.
- Clean Up folders - a new Clean Up button in the Known Folders section removes any folder that has no groups associated with it, after a confirmation prompt showing the count to be removed.
- Storage usage indicator - the dialog now shows how much of the 10 MB storage.local quota is in use, with a colour-coded progress bar (blue → orange at 70% → red at 90%).