feat: restore mentor page to final day/night spec

Rebuild the mentor workspace per the approved final design (day.png/night.png):
- mentorView gets a dedicated full-width immersive shell (independent 56px
  top bar with page title slot + theme mode text, hidden module-nav/market
  tape/overview/status bar) scoped to body[data-active-view=mentorView].
- Assistant messages become borderless body text with name/time above; only
  user messages use a blue bubble; keep loading/error/streaming caret states.
- 4 quick topics stay visible with history; composer restored to a framed
  ~94px card with bottom-left shortcut hint and bottom-right send button.
- Directory tools merged into one row (search + filter menu + sort); the
  filter menu still offers all/A/B/C; list selected state is an inset rounded
  fill; contact rows are borderless 75px items.
- Chat header always shows pin/note/profile/clear; pin reuses /api/mentors/
  preferences; theme toggle stays the single #themeToggle.
- Night tokens match the spec including the two distinct blues (#316FEF link,
  #5B8DEF quote/selected icon). Mobile (<768) stacks panels with no horizontal
  overflow; 1024+ follows the desktop spec.
- Update stale test baselines (300px sidebar, 94px composer, hint presence,
  night bubble color, centered disclaimer) and regenerate the architecture
  inventory.

Co-authored-by: multica-agent <github@multica.ai>

frontend/shared/tokens.css

@@ -219,13 +219,12 @@
   --dragon-profile-weight-strong: 750;
   --dragon-profile-weight-semibold: 600;
 
-  --mentor-directory-width: 280px;
-  --mentor-profile-width: 272px;
-  --mentor-pane-header-height: 58px;
-  --mentor-avatar-size: 38px;
+  --mentor-directory-width: 300px;
+  --mentor-pane-header-height: 60px;
+  --mentor-avatar-size: 42px;
   --mentor-profile-avatar-size: 68px;
   --mentor-composer-min-height: 94px;
-  --mentor-message-max-width: 82%;
+  --mentor-message-max-width: 60%;
 
   --chart-background: #fbfcfd;
   --chart-grid: #e2e8ec;