cleanup: extract .section-title flex layout + .section-title-label

The sidebar's streamer section-title carried two inline flex containers:
- outer .section-title with display:flex; align-items:center; gap:6px; justify-content:space-between (so the bulk-remove X button can pin right while the title group stays left)
- inner span with display:flex; align-items:baseline; gap:8px (so the title text and the streamer counter share the same text-baseline rather than centring against each other)

.section-title is only used in this one spot, so the flex layout becomes part of the class definition (no risk of bleeding into other usages). The inner-span pattern moves to a dedicated .section-title-label class. Two inline style attributes gone.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/index.html

@@ -216,8 +216,8 @@
                 </div>
             </nav>
 
-            <div class="section-title" id="streamerSectionTitle" style="display:flex; align-items:center; gap:6px; justify-content:space-between;">
-                <span style="display:flex; align-items:baseline; gap:8px;">
+            <div class="section-title" id="streamerSectionTitle">
+                <span class="section-title-label">
                     <span id="streamerSectionTitleText">Streamer</span>
                     <span id="streamerSectionCounter" class="streamer-section-counter"></span>
                 </span>