fix: replace monospaced ALL CAPS labels with Inter sentence case

Remove IBM Plex Mono + text-transform: uppercase from all UI labels.
CSS classes .font-mono-label and .font-mono-overline now use Inter
with no text-transform. Inline monospace+uppercase styles in
StatusDropdown, TagsDropdown, ReferencedByPanel, AiActionCard replaced.
Tailwind uppercase removed from Sidebar, CommandPalette, PulseView,
CreateNoteDialog, CreateTypeDialog. Hardcoded ALL CAPS text (COLOR,
ICON, TEMPLATE) converted to sentence case. Code blocks and commit
hashes remain monospaced.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/Sidebar.tsx

@@ -315,7 +315,7 @@ export const Sidebar = memo(function Sidebar({
         {/* Sections header + visibility popover */}
         <div ref={customizeRef} style={{ position: 'relative', padding: '4px 6px 0' }}>
           <div className="flex w-full select-none items-center justify-between" style={{ padding: '4px 16px' }}>
-            <span className="text-[11px] font-semibold uppercase tracking-wider text-muted-foreground">Sections</span>
+            <span className="text-[11px] font-medium text-muted-foreground">Sections</span>
             <button className="flex shrink-0 cursor-pointer items-center justify-center rounded border-none bg-transparent p-0 text-muted-foreground transition-colors hover:text-foreground" style={{ width: 20, height: 20 }} onClick={() => setShowCustomize((v) => !v)} aria-label="Customize sections" title="Customize sections">
               <SlidersHorizontal size={14} />
             </button>