0.8.2: pan outside canvas + finish RUWIO rename of exports

- Canvas stage: plain left-click in the empty content area (outside
  the canvas rectangle) now starts a pan. Ctrl+left-click still pans
  anywhere, middle-click unchanged. Only pure left-click qualifies
  (any modifier leaves the old routing intact).
- Export rebrand Animatr → RUWIO for everything user-visible:
  - Default filenames: projekt.animatr.json → projekt.ruwio.json;
    animatr-runtime.js → ruwio-runtime.js; App's export fallback
    base animatr → ruwio.
  - Generated comment headers in runtime/scene/bundled scripts.
  - Console warn prefix in the runtime and the scene store.
  - Example HTML title, heading, and embed-usage snippet.
  - parseProject error message.
  - ExportDialog copy.
- RUNTIME_VERSION 14 → 15 so cached runtimes reload.
- On-disk magic stays `animatr-project` and window.AnimatrPlayer /
  __animatrPending / localStorage & IndexedDB keys are untouched so
  old project files and previously-exported HTML keep working.

Regression tests: legacy magic still parses; parseProject error
mentions RUWIO and not Animatr; runtime/scene/bundled scripts and
example HTML all carry the new brand; console prefix is [ruwio].

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

src/components/ExportDialog.vue

@@ -135,7 +135,7 @@ function onUpdate(v: boolean) {
         <div class="opt-icon"><PhEngine :size="20" /></div>
         <div class="opt-text">
           <div class="opt-title">
-            animatr-runtime.js
+            ruwio-runtime.js
             <span class="badge">{{ t('export.runtimeBadge') }}</span>
           </div>
           <div class="opt-desc">{{ t('export.runtimeDesc') }}</div>