M10 (task 2013): integrated AppImage — app self-integration (OOBE + Account toggle)

The Linux AppImage can now install itself into the applications menu, so it behaves
like an installed app instead of a loose file.

- Rust (desktop/src-tauri/src/integration.rs): integration_status / integrate_desktop
  / unintegrate_desktop commands — detect $APPIMAGE, copy the AppImage to
  ~/Applications, write ~/.local/share/applications/thoughtsync.desktop + embedded
  icon, update-desktop-database. Registered in lib.rs.
- Frontend: withGlobalTauri exposes window.__TAURI__.core.invoke; desktop/bridge.ts
  (isDesktop + typed invoke, NO @tauri-apps/api dep -> web bundle unaffected);
  DesktopIntegrationPrompt (first-run OOBE, remembered) mounted in App.vue;
  AccountView "Desktop app" add/remove control. All desktop-guarded -> no-ops on web.
- desktop.yml: upload the .deb + .AppImage as a run artifact (continue-on-error) so
  the build is downloadable for hand-testing.

Verified by CI: ci.yml (vue-tsc) for the frontend, desktop.yml (cargo + tauri build)
for the Rust + AppImage.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

frontend/src/components/DesktopIntegrationPrompt.vue

@@ -0,0 +1,71 @@
+<script setup lang="ts">
+import { onMounted, ref } from "vue";
+import BaseModal from "./BaseModal.vue";
+import BaseButton from "./BaseButton.vue";
+import { isDesktop, desktop } from "../desktop/bridge";
+import { useUiStore } from "../stores/ui";
+
+// First-run prompt (Linux AppImage only) offering to add ThoughtSync to the
+// applications menu so it behaves like an installed app instead of a loose file.
+// Shown once; the choice is remembered. Users who decline can integrate later from
+// Account. No-op on the web build and on already-integrated / non-AppImage runs.
+const DISMISS_KEY = "desktop.integration.prompted";
+
+const ui = useUiStore();
+const show = ref(false);
+const working = ref(false);
+
+onMounted(async () => {
+  if (!isDesktop() || localStorage.getItem(DISMISS_KEY)) return;
+  try {
+    const status = await desktop.integrationStatus();
+    if (status.is_appimage && !status.is_integrated) show.value = true;
+  } catch {
+    /* not an AppImage / no bridge — just don't prompt */
+  }
+});
+
+function dismiss() {
+  localStorage.setItem(DISMISS_KEY, "1");
+  show.value = false;
+}
+
+async function integrate() {
+  working.value = true;
+  try {
+    await desktop.integrate();
+    localStorage.setItem(DISMISS_KEY, "1");
+    show.value = false;
+    ui.showToast("ThoughtSync added to your applications menu.");
+  } catch (e) {
+    ui.showToast((e as { message?: string }).message ?? "Couldn't add to applications.");
+  } finally {
+    working.value = false;
+  }
+}
+</script>
+
+<template>
+  <BaseModal
+    v-if="show"
+    align="center"
+    panel-class="w-full max-w-md shadow-xl"
+    aria-label="Add ThoughtSync to your applications"
+    @close="dismiss"
+  >
+    <div class="p-6">
+      <h2 class="text-lg font-bold tracking-tight text-neutral-900 dark:text-neutral-100">
+        Add ThoughtSync to your applications?
+      </h2>
+      <p class="mt-2 text-sm text-neutral-600 dark:text-neutral-400">
+        We'll add a menu entry so you can launch ThoughtSync from your app launcher, and keep a stable
+        copy in <code class="font-mono text-xs">~/Applications</code> so it isn't lost from Downloads.
+        You can undo this any time from your account.
+      </p>
+      <div class="mt-6 flex justify-end gap-3">
+        <BaseButton variant="ghost" :disabled="working" @click="dismiss">Not now</BaseButton>
+        <BaseButton :loading="working" @click="integrate">Add to applications</BaseButton>
+      </div>
+    </div>
+  </BaseModal>
+</template>