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/lib/changelog.js

@@ -6,10 +6,18 @@
 //   - Add a CHANGELOG entry only when a commit changes something players can
 //     see. Skip refactors, tests, and tooling. Keep wording player-facing.
 
-export const VERSION = 6;
+export const VERSION = 7;
 
 // Newest first. Each entry: { version, date: 'YYYY-MM-DD', changes: [string, ...] }.
 export const CHANGELOG = [
+    {
+        version: 7,
+        date: '2026-06-15',
+        changes: [
+            'During a scene, the Event Log can be collapsed to a corner button to declutter your screen, and reopened from that button.',
+            'In the three-column layout, the Event Log now stays pinned within the screen and scrolls internally, so its newest entries are always visible.',
+        ],
+    },
     {
         version: 6,
         date: '2026-06-15',