Make the inline Event Log collapsible and viewport-bounded (v7)

Two scene-layout tweaks to the inline (third-column) Event Log:

- It can now be collapsed to a fixed corner button (✕ in its header) to declutter,
  and reopened from that button. ScenePhase owns `logOpen` and reflows the grid to
  two columns while collapsed; EventLog dispatches `collapse`.
- The panel now pins at top:3.5rem (matching .dashboard-container's top padding)
  with max-height calc(100vh - 4.5rem), so its bottom stays on-screen at any scroll
  position and .log-content scrolls internally — previously the bottom sat ~24px
  below the fold at the top of the page.

Verified across Pi-Rat and Deep views, scroll extremes, and 3-col / 1-col widths.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/assets/css/scene-play.css

@@ -17,6 +17,34 @@
     align-self: stretch;
 }
 
+/* When the inline log is collapsed, reclaim its column (3-col layout only). */
+@media (min-width: 1101px) {
+    .scene-view-layout.log-collapsed {
+        grid-template-columns: 180px minmax(0, 1fr);
+    }
+}
+
+/* Corner button that reopens the collapsed inline Event Log. */
+.log-reopen-btn {
+    position: fixed;
+    bottom: 20px;
+    right: 20px;
+    z-index: 1000;
+    padding: 10px 14px;
+    background: color-mix(in srgb, var(--bg-deep) 95%, transparent);
+    border: 1px solid var(--edge);
+    border-radius: var(--radius-md);
+    box-shadow: var(--shadow-deep);
+    color: var(--text);
+    font-weight: bold;
+    font-family: var(--font-heading);
+    cursor: pointer;
+    backdrop-filter: blur(10px);
+}
+.log-reopen-btn:hover {
+    background: color-mix(in srgb, var(--accent) 12%, var(--bg-deep));
+}
+
 @media (max-width: 1100px) {
     .scene-view-layout {
         grid-template-columns: 1fr;