feat(app): GUI backlog — splitter, drag-reorder, fit, persist, modal focus

- LayoutEngine: fix splitter resize (track pointer 1:1 via delta-from-start)
  and add panel drag-to-reorder using raw pointer events with drop indicators
- TerminalView: auto-fit xterm to container via FitAddon + ResizeObserver
- App/TopBar: toggleable sidebar; persist sidebar/events collapse in
  localStorage; bell icon opens the activity log
- Wizard: new-workspace modal now grabs focus and handles keyboard
- deps: add @xterm/addon-fit

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/package-lock.json

@@ -12,6 +12,7 @@
         "@fontsource/inter": "^5.2.8",
         "@tauri-apps/api": "^2",
         "@tauri-apps/plugin-notification": "^2",
+        "@xterm/addon-fit": "^0.10.0",
         "@xterm/addon-search": "^0.16.0",
         "@xterm/addon-webgl": "^0.18.0",
         "@xterm/xterm": "^5.5.0",
@@ -1463,6 +1464,15 @@
         "vite": "^4.2.0 || ^5.0.0 || ^6.0.0 || ^7.0.0"
       }
     },
+    "node_modules/@xterm/addon-fit": {
+      "version": "0.10.0",
+      "resolved": "https://registry.npmjs.org/@xterm/addon-fit/-/addon-fit-0.10.0.tgz",
+      "integrity": "sha512-UFYkDm4HUahf2lnEyHvio51TNGiLK66mqP2JoATy7hRZeXaGMRDr00JiSF7m63vR5WKATF605yEggJKsw0JpMQ==",
+      "license": "MIT",
+      "peerDependencies": {
+        "@xterm/xterm": "^5.0.0"
+      }
+    },
     "node_modules/@xterm/addon-search": {
       "version": "0.16.0",
       "resolved": "https://registry.npmjs.org/@xterm/addon-search/-/addon-search-0.16.0.tgz",