fix(web): companion-gate the store banner + manual intro trigger (#61 residual)

Only the auto-popup was companion-gated — inside the companion WebView
users still saw the 'install the companion' banner in the App Store and
could pop the intro overlay through it. Gates all three paths on
isCompanionApp(): CompanionBanner self-hides, openCompanionIntro() is a
no-op, and the manual-open watcher in CompanionIntroOverlay refuses to
open (the overlay's raw window check also moves to the canonical helper
so there is exactly one detection). No APK change.

neode-ui/src/composables/useCompanionIntro.ts

@@ -1,13 +1,20 @@
 import { ref } from 'vue'
 
+import { isCompanionApp } from '@/utils/openExternal'
+
 /**
  * Cross-view trigger for the Remote Companion intro/pairing modal
  * (CompanionIntroOverlay, mounted once in Dashboard.vue). Views like the
  * App Store banner call openCompanionIntro() to pop it on demand — this
  * bypasses the once-per-browser auto-show gate.
+ *
+ * Inside the companion app's own WebView the whole pitch is nonsense — the
+ * user is already running it — so the trigger is a no-op there (#61: the
+ * auto-popup was gated, this manual path and CompanionBanner weren't).
  */
 export const companionIntroRequested = ref(false)
 
 export function openCompanionIntro(): void {
+  if (isCompanionApp()) return
   companionIntroRequested.value = true
 }