Route terminal clipboard through tauri-plugin-clipboard-manager; bump to 0.2.3

navigator.clipboard.readText() triggers WebView2's "Allow clipboard access?"
permission prompt on every paste. The plugin goes through IPC + the OS
clipboard directly, so the prompt never fires.

Wired the Rust plugin, granted clipboard-manager:allow-{read,write}-text in
the capabilities manifest, swapped XtermPane's copy/paste handler to use
the plugin's readText/writeText.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src-tauri/capabilities/default.json

@@ -6,6 +6,8 @@
   "permissions": [
     "core:default",
     "core:event:default",
-    "core:window:default"
+    "core:window:default",
+    "clipboard-manager:allow-read-text",
+    "clipboard-manager:allow-write-text"
   ]
 }