fix: add Tauri v2 capabilities — unblock event:listen for SSH terminal

The app had no capabilities file, so Tauri v2's ACL blocked all
frontend listen() calls. SSH connections succeeded on the Rust side
but the terminal never received data events, appearing as "nothing
happened." Grants core:default, core:event:default, core🪟default,
and shell:allow-open.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src-tauri/capabilities/default.json

@@ -0,0 +1,11 @@
+{
+  "identifier": "default",
+  "description": "Default capabilities for the main Wraith window",
+  "windows": ["main"],
+  "permissions": [
+    "core:default",
+    "core:event:default",
+    "core:window:default",
+    "shell:allow-open"
+  ]
+}