fix(canvas): use vertical-align: top to eliminate baseline gap (#5484)

* fix(canvas): make graph canvas block-level to eliminate baseline gap

- Change <canvas id=graph-canvas> to display:block via Tailwind class
- Removes 1–5 px baseline offset between canvas and container
- Aligns canvas and TransformPane origins; fixes link/slot endpoint drift

No behavioral changes beyond layout origin alignment; no dependent CSS relies on inline/baseline.

* switch block to align-top

* Update test expectations [skip ci]

* Revert "Update test expectations [skip ci]"

This reverts commit ee0dfd4e0a.

* empty commit for ci

* Update test expectations [skip ci]

---------

Co-authored-by: github-actions <github-actions@github.com>

src/components/graph/GraphCanvas.vue

@@ -28,7 +28,7 @@
     id="graph-canvas"
     ref="canvasRef"
     tabindex="1"
-    class="w-full h-full touch-none"
+    class="align-top w-full h-full touch-none"
   />
 
   <!-- TransformPane for Vue node rendering -->