feat: mirror pane (p), cursor memory, clean up help dialog

- Add Mirror pane keybinding p (for 'Pane'), SSH restored on s
- Add session-scoped cursor memory per directory
- Fix cursor memory bug: DisplayName() adds trailing / for directories
- Fix remote mirror: use active.Path instead of mount.RemotePath
- Remove F-key/Mouse/b/c entries from F1 help dialog
- Remove Mirror from ShortHelp footer (F-keys only)
- Add missing letter-key bindings to help: p, s, a, n, x

vcom.toml

@@ -4,7 +4,7 @@ right_path = ''
 
 [ui]
 app_title = 'vcom'
-theme = 'one-dark'
+theme = 'ayu-dark'
 icon_mode = 'auto'
 show_title_bar = true
 show_footer = true