feat(v2): implement session persistence, file watcher, and markdown viewer

Phase 4 complete (MVP ship):
- SessionDb (rusqlite, WAL mode): sessions + layout_state tables, CRUD
- FileWatcherManager (notify v6): watch files, emit Tauri change events
- MarkdownPane: marked.js rendering with Catppuccin styles, live reload
- Layout store wired to persistence (addPane/removePane/setPreset persist)
- restoreFromDb() on startup restores panes in layout order
- Sidebar "M" button opens file picker for markdown files
- New adapters: session-bridge.ts, file-bridge.ts
- Deps: rusqlite (bundled), dirs 5, notify 6, marked

v2/package-lock.json

@@ -11,7 +11,8 @@
         "@tauri-apps/api": "^2.10.1",
         "@xterm/addon-canvas": "^0.7.0",
         "@xterm/addon-fit": "^0.11.0",
-        "@xterm/xterm": "^6.0.0"
+        "@xterm/xterm": "^6.0.0",
+        "marked": "^17.0.4"
       },
       "devDependencies": {
         "@sveltejs/vite-plugin-svelte": "^6.2.1",
@@ -1174,6 +1175,18 @@
         "@jridgewell/sourcemap-codec": "^1.5.5"
       }
     },
+    "node_modules/marked": {
+      "version": "17.0.4",
+      "resolved": "https://registry.npmjs.org/marked/-/marked-17.0.4.tgz",
+      "integrity": "sha512-NOmVMM+KAokHMvjWmC5N/ZOvgmSWuqJB8FoYI019j4ogb/PeRMKoKIjReZ2w3376kkA8dSJIP8uD993Kxc0iRQ==",
+      "license": "MIT",
+      "bin": {
+        "marked": "bin/marked.js"
+      },
+      "engines": {
+        "node": ">= 20"
+      }
+    },
     "node_modules/mri": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/mri/-/mri-1.2.0.tgz",