feat: BooCode 2.0 UI — Ember theme, brand banner, coder tabs, model-attribution chips

- Ember theme (Obsidian charcoal + #ff7a18 orange), now DEFAULT_THEME_ID; server theme_id whitelist gains 'ember'
- Brand banner: transparent Westie mascot + >_BooCode wordmark, big/edge-to-edge (flood-filled to transparency + cropped)
- Coder panes are multi-tab: + opens a BooCode tab, split opens a pane (shared ChatTabBar via tabKind + createCoderTab; closeOtherTabs/tab-numbering extended to coder)
- Model-attribution: new messages.model column stamped at finalizeCompletion (BooChat/native coder) + dispatcher assistant-row creation (external coder); surfaced via view + wire types + live frame; rendered as a subtle shortened-name chip (shortenModelName)
- Composer Web toggle moved into a boxed focus-ringed input; glowing accent dot on tool rows
- Claude SDK follow-ups (1M context, follow-up-message fix, collapsed thinking/tool chips) + CLAUDE_SDK_BACKEND=1

apps/web/src/components/ToolCallLine.tsx

@@ -149,8 +149,13 @@ export function ToolCallLine({ run, insideGroup }: Props) {
         onClick={() => setOpen((v) => !v)}
         className="flex items-center gap-1.5 w-full text-left hover:bg-muted/40 rounded px-1 py-0.5 -mx-1"
       >
+        {/* BooCode 2.0: glowing activity indicator (was ↳ / >_) */}
         {!insideGroup && (
-          <span className="text-muted-foreground/60 select-none shrink-0">↳</span>
+          <span
+            className="size-1.5 rounded-full bg-primary shrink-0"
+            style={{ boxShadow: '0 0 6px var(--primary)' }}
+            aria-hidden
+          />
         )}
         <ChevronRight
           className={`size-3 text-muted-foreground/60 shrink-0 transition-transform ${open ? 'rotate-90' : ''}`}