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>

todo

@@ -144,4 +144,6 @@ warum ist eigentlich still frame easing disabled? man muss doch zu einem still-f
 
  ich würde an dieser stelle mal ein paar regression-tests hinzufügen und dann committen
 
-wenn man den leeren teil des content-views zieht (außerhalb der canvas constraints) muss canvas move auch ohne control key gehen
+wenn man den leeren teil des content-views zieht (außerhalb der canvas constraints) muss canvas move auch ohne control key gehen
+
+export dateien heißen noch animatr. wir haben in RUWIO umbenannt