feat: add auto-memory panel, /memory command, and unified toast system

- Add /memory CLI built-in slash command
- Refactor MemoryBrowserPanel to accept isOpen/onClose props
- Add Send /memory and Refresh buttons to MemoryBrowserPanel header
- Add Memory Manager entry to NavMenu
- Create unified ToastContainer replacing AchievementNotification and
  UpdateNotification with a single stacked toast system
- Add toasts store with info (4s), achievement (5s), and persistent
  update toast types
- Move getAchievementRarity and getRarityColour helpers to toasts store
- Detect auto-memory writes in tauri.ts output listener and fire toast
- Remove action buttons from update toast; version is now a direct link

Closes #212

src/lib/tauri.ts

@@ -23,6 +23,7 @@ import {
   handleNewUserMessage,
 } from "$lib/notifications/rules";
 import { notificationManager } from "$lib/notifications/notificationManager";
+import { toastStore } from "$lib/stores/toasts";
 
 interface StateChangePayload {
   state: CharacterState;
@@ -431,6 +432,16 @@ export async function initializeTauriListeners() {
         parent_tool_use_id
       );
     }
+
+    // Detect auto-memory updates — tool writes to ~/.claude/ markdown files
+    if (
+      line_type === "tool" &&
+      content &&
+      content.includes("/.claude/") &&
+      content.includes(".md")
+    ) {
+      toastStore.addInfo("Auto-memory updated", "🧠");
+    }
   });
   unlisteners.push(outputUnlisten);