fix(live-state): eliminate flash on poll by switching to innerHTML swap

outerHTML removes and re-inserts the section on each tick, causing a
blank frame. Keeping the <section> as a stable DOM container and
swapping only innerHTML means avatars and text update in-place without
any teardown/reconstruct cycle.

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

l4d2web/templates/_live_state.html

@@ -1,65 +1,60 @@
-<section class="panel live-state"
-         hx-get="/servers/{{ server.id }}/live-state"
-         hx-trigger="every {{ poll_seconds }}s"
-         hx-swap="outerHTML">
-  <h2 class="section-title">Live state</h2>
-  {% if not snapshot or not snapshot_fresh %}
-    <p class="muted">No data — server is not currently reporting.</p>
-  {% else %}
-    <p class="server-live-summary">
-      {{ snapshot.players }}/{{ snapshot.max_players }}
-      {% if snapshot.hibernating %}· idle{% endif %}
-      · {{ snapshot.map }}
-      <small class="muted">
-        polled {{ ((now - snapshot.last_seen_at).total_seconds() | int) }}s ago
-      </small>
-    </p>
-  {% endif %}
+<h2 class="section-title">Live state</h2>
+{% if not snapshot or not snapshot_fresh %}
+  <p class="muted">No data — server is not currently reporting.</p>
+{% else %}
+  <p class="server-live-summary">
+    {{ snapshot.players }}/{{ snapshot.max_players }}
+    {% if snapshot.hibernating %}· idle{% endif %}
+    · {{ snapshot.map }}
+    <small class="muted">
+      polled {{ ((now - snapshot.last_seen_at).total_seconds() | int) }}s ago
+    </small>
+  </p>
+{% endif %}
 
-  {% if current_players %}
-    <h3 class="section-subtitle">Current players</h3>
-    <ul class="player-grid">
-      {% for session, profile in current_players %}
-        <li class="player-card">
-          <a class="player-link"
-             href="https://steamcommunity.com/profiles/{{ session.steam_id_64 }}"
-             target="_blank" rel="noopener noreferrer">
-            {% if profile and profile.avatar_url %}
-              <img class="avatar" src="{{ profile.avatar_url }}" alt="" loading="lazy">
-            {% else %}
-              <span class="avatar placeholder" aria-hidden="true"></span>
-            {% endif %}
-            <span class="name">{{ (profile and profile.persona_name) or session.name_at_join }}</span>
-          </a>
-          <span class="meta">
-            joined {{ ((now - session.joined_at).total_seconds() // 60) | int }}m ago
-            · ping {{ session.min_ping }}-{{ session.max_ping }}ms
-          </span>
-        </li>
-      {% endfor %}
-    </ul>
-  {% endif %}
+{% if current_players %}
+  <h3 class="section-subtitle">Current players</h3>
+  <ul class="player-grid">
+    {% for session, profile in current_players %}
+      <li class="player-card">
+        <a class="player-link"
+           href="https://steamcommunity.com/profiles/{{ session.steam_id_64 }}"
+           target="_blank" rel="noopener noreferrer">
+          {% if profile and profile.avatar_url %}
+            <img class="avatar" src="{{ profile.avatar_url }}" alt="" loading="lazy">
+          {% else %}
+            <span class="avatar placeholder" aria-hidden="true"></span>
+          {% endif %}
+          <span class="name">{{ (profile and profile.persona_name) or session.name_at_join }}</span>
+        </a>
+        <span class="meta">
+          joined {{ ((now - session.joined_at).total_seconds() // 60) | int }}m ago
+          · ping {{ session.min_ping }}-{{ session.max_ping }}ms
+        </span>
+      </li>
+    {% endfor %}
+  </ul>
+{% endif %}
 
-  {% if recent_players %}
-    <h3 class="section-subtitle">Recent players</h3>
-    <ul class="player-grid recent">
-      {% for row in recent_players %}
-        <li class="player-card">
-          <a class="player-link"
-             href="https://steamcommunity.com/profiles/{{ row.steam_id_64 }}"
-             target="_blank" rel="noopener noreferrer">
-            {% if row.avatar_url %}
-              <img class="avatar" src="{{ row.avatar_url }}" alt="" loading="lazy">
-            {% else %}
-              <span class="avatar placeholder" aria-hidden="true"></span>
-            {% endif %}
-            <span class="name">{{ row.persona_name or row.name_at_join }}</span>
-          </a>
-          <span class="meta">
-            last seen {{ ((now - row.last_seen).total_seconds() // 60) | int }}m ago
-          </span>
-        </li>
-      {% endfor %}
-    </ul>
-  {% endif %}
-</section>
+{% if recent_players %}
+  <h3 class="section-subtitle">Recent players</h3>
+  <ul class="player-grid recent">
+    {% for row in recent_players %}
+      <li class="player-card">
+        <a class="player-link"
+           href="https://steamcommunity.com/profiles/{{ row.steam_id_64 }}"
+           target="_blank" rel="noopener noreferrer">
+          {% if row.avatar_url %}
+            <img class="avatar" src="{{ row.avatar_url }}" alt="" loading="lazy">
+          {% else %}
+            <span class="avatar placeholder" aria-hidden="true"></span>
+          {% endif %}
+          <span class="name">{{ row.persona_name or row.name_at_join }}</span>
+        </a>
+        <span class="meta">
+          last seen {{ ((now - row.last_seen).total_seconds() // 60) | int }}m ago
+        </span>
+      </li>
+    {% endfor %}
+  </ul>
+{% endif %}

l4d2web/templates/server_detail.html

@@ -22,7 +22,7 @@
   <section class="panel live-state"
            hx-get="/servers/{{ server.id }}/live-state"
            hx-trigger="load, every 5s"
-           hx-swap="outerHTML">
+           hx-swap="innerHTML">
   </section>
 
   <h2 class="section-title">Files</h2>