refactor(frontend): delete the dead CSS the consumer map surfaced — 102 classes, 588 lines (#2962)

Milestone 302's map flagged 195 css rows no template names. Re-derived the
list locally with a stricter test than the map's — a class is dead only if
its token appears NOWHERE outside a <style> block, in markup or script, and
is not the static half of a concatenated name (`priority-${p}`) — which
takes the map's known blind spot off the table. 123 survived that; 21 of
those are Vue <Transition>/<transition-group> classes generated at runtime
from a name= attribute (detail-fade, peek-slide, shortcuts-fade, tab-fade,
toast) and one is ProseMirror's vendor class. Those stay. The other 102 go.

- SettingsView.vue (80, -417 lines): whole features whose UI was removed —
  Ollama model management (model-*, pull-bar-*, suggestion-chip), push
  notifications (push-*), the voice library and voice blending (voice-*,
  blend-*), geo status (geo-*), MCP package rows, retention, the learned
  summary, and the form furniture that served them.
- editor-shared.css (16, -151): the standalone assist panel, superseded by
  the sidebar assist section — streaming now renders as .stream-preview in
  the main area, so .assist-panel*, .assist-sections*, .assist-preview-box
  and .typing-indicator have no markup left. @keyframes blink went with the
  last rule that animated it. .editor-body/.editor-main are dead too:
  TaskEditorView replaced them with .task-body/.task-main.
- theme.css: .btn-new-conv/.btn-send dropped from the touch-target list
  (names from another app), and the .hide-desktop utility no one used. The
  generated --fs-* token block is untouched.
- ShareDialog .user-result-email, KnowledgeView .today-link,
  ProjectView .edit-input (the remainder rule keeps its rationale comment
  and its two live selectors).

A selector dies only when every class in its descendant chain is checked —
`.live .dead` matches nothing either — and a rule only when its whole comma
list is dead, so mixed lists keep their live half. Template and script
regions are byte-identical; check_dangling_styles.py and
check_design_tokens.py both pass, with only the six pre-existing reports.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/assets/theme.css

@@ -272,17 +272,10 @@ button:not(:disabled):active,
     display: none !important;
   }
   button,
-  [role="button"],
-  .btn-new-conv,
-  .btn-send {
+  [role="button"] {
     min-height: 44px;
   }
 }
-@media (min-width: 769px) {
-  .hide-desktop {
-    display: none !important;
-  }
-}
 
 /* Neutral hairline scrollbars — chrome is structural, not branded */
 ::-webkit-scrollbar {