fix(typography): strip chrome italic; reserve italic for emphasis

Per the design rule "italic is for emphasis, not for design", removed
every chrome `font-style: italic` declaration across the frontend.
42 declarations gone across 24 files: empty-state placeholder copy,
loading messages, "no results" hints, ghost text, voice/role labels,
field placeholder text, brand wordmark, et al.

Markdown content emphasis is unaffected — `<em>` and `<i>` tags from
`*emphasis*` markup still render italic via browser default styling
(prose.css doesn't override em behavior). User-typed emphasis in
notes, journal entries, and chat messages keeps its italic.

Specific spots that lost the decorative italic:

- KnowledgeView .filter-label, .empty-narrator
- NoteEditorView .ef-label, link-suggest related
- ChatPanel .empty-msg, .empty-greeting, .role-label
- ChatMessage .role-assistant .role-label (the "Fable" voice tag —
  was italic per the doc's Illuminated Transcript spec, but per the
  new typography rule the speaker tag stays regular and lets the
  border-left + glow do the bubble framing on their own)
- AppHeader .brand-text ("Fabled" wordmark)
- editor-shared.css .title-input::placeholder
- ProjectView .project-title-input::placeholder
- HomeView .urgency-loading
- WorkspaceTaskPanel .empty-group
- WeatherCard .weather-unavailable
- SharedWithMeView .empty-msg
- DiffView empty-state spans
- ToolCallCard .tool-event-more
- SettingsView 7 spots (.you-label, .geo-pending, hint text, etc.)
- + several other empty-state / hint text spots

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/components/WorkspaceTaskPanel.vue

@@ -495,7 +495,7 @@ defineExpose({ reload: loadAll });
   flex-shrink: 0;
 }
 
-.empty-group { padding: 0.4rem 1.4rem; font-size: 0.78rem; color: var(--color-text-muted); font-style: italic; }
+.empty-group { padding: 0.4rem 1.4rem; font-size: 0.78rem; color: var(--color-text-muted); }
 
 .state-msg { padding: 1.5rem; text-align: center; font-size: 0.85rem; color: var(--color-text-muted); }