Unify font sizes through qs.Commons.Style

Themes now drive typography the same way they drive colors: one [font]
base-size in shell.toml is the rem root, and every Style.font.<token>
(caption, bodySmall, body, subtitle, title, heading, display,
displayLarge, iconSmall, icon, iconLarge) derives from it via a fixed
multiplier. Themes can also pin individual tokens for stylistic
emphasis. base-size is clamped 11..13 until row-height tokens exist.

Bar dimensions move to the same singleton: [bar] size-horizontal /
size-vertical replace the hardcoded 26/28 in Bar.qml, exposed as
Style.bar.sizeHorizontal / sizeVertical.

Style.qml also resolves the fontconfig 'monospace' alias via fc-match
and exposes Style.font.resolvedFamily so panels can display the
concrete family. Watches ~/.config/fontconfig/fonts.conf so it tracks
'omarchy font set <name>'.

The qs.Ui kit (PillButton, Dropdown, Toggle, TextField, etc.) and
every first-party plugin (bar widgets, settings, menu, clipboard,
emoji, polkit, notifications, osd, image-picker, dev-gallery) now
bind to Style.font.* instead of pixel literals. Only three deliberate
display-scale outliers remain: the notification empty-state glyph and
the weather flyout's hero temperature pair, all commented.

Background plugin's applyTheme IPC fast-path also pushes shell.toml to
Style so theme swaps update typography and bar size without waiting
for inotify debounce.

Dev gallery (omarchy dev ui-preview) now ships a Typography section
that renders the full scale and theme tokens live, and its summon
command is fixed (omarchy-shell-ipc -> omarchy-shell).

shell/plugins/image-picker/ImagePicker.qml

@@ -642,7 +642,7 @@ Item {
           color: root.foreground
           style: Text.Outline
           styleColor: root.withAlpha(root.background, 0.7)
-          font.pixelSize: 24
+          font.pixelSize: Style.font.display
           font.weight: Font.DemiBold
           horizontalAlignment: Text.AlignHCenter
           elide: Text.ElideRight
@@ -659,7 +659,7 @@ Item {
           opacity: 0.85
           style: Text.Outline
           styleColor: root.withAlpha(root.background, 0.7)
-          font.pixelSize: 14
+          font.pixelSize: Style.font.title
           horizontalAlignment: Text.AlignHCenter
           elide: Text.ElideRight
         }