P0: scaffold Vite + Vue 3 + Tauri v2

- pnpm + TS + Tailwind 3 + Pinia + Vue Router with hash history
- 6 placeholder views (Status, Peers, Routes, Messages, Topics, Settings)
  rendered via lucide-icon sidebar in App.vue
- Tauri v2: shell, store, log, dialog plugins; bundle targets deb +
  appimage; sidecar wired via externalBin = binaries/mycelium
- scripts/fetch-mycelium.sh pins v0.6.1, maps musl asset onto
  gnu target triple expected by Tauri bundler
- CI: pnpm typecheck + cargo fmt/clippy/test

src-tauri/capabilities/default.json

@@ -0,0 +1,12 @@
+{
+  "$schema": "../gen/schemas/desktop-schema.json",
+  "identifier": "default",
+  "description": "Capabilities for the main window. The mycelium sidecar is spawned from Rust setup and does not require JS-side shell permissions.",
+  "windows": ["main"],
+  "permissions": [
+    "core:default",
+    "store:default",
+    "log:default",
+    "dialog:default"
+  ]
+}