[ttncode]

Summary

User feedback fixes:

• Reset asks first. Resetting an unfinished focus session (button or Alt+R) now confirms: "Time focused so far won't count toward today." A finished session resets without asking, since its time is already saved.
• Keyboard Shortcuts in the menu. New Settings item opens the shortcuts list (previously only reachable with Ctrl+/).
• Shortcuts list no longer focuses Done. Focus goes to the dialog itself: no focus ring on Done, Enter can't close it by accident, Esc still closes.
• Extension opens in its own window with a taskbar icon. The toolbar button now opens popup.html in a popup window (same approach as Notelet) instead of Chrome's dropdown. It gets its own Windows taskbar entry with the extension icon, stays open when it loses focus, is single-instance, and remembers its size and position. The popup layout now fills the window instead of a fixed 400x600.

Testing

• Lint, typecheck, unit tests and build pass; build:extension manifest has no default_popup.
• Browser (static build): menu item opens the panel with focus on the dialog; Reset during a running session shows the confirm.
• Not tested: the extension window and taskbar icon on Windows.