fix: make graph canvas toolbar visible on mobile (#10168)

## Summary

Fix the bottom-right graph canvas toolbar (zoom controls, fit-to-view,
minimap toggle) not being visible on mobile devices in normal graph
mode.

## Problem

PrimeVue applies `overflow: hidden` to all `.p-splitterpanel` elements
by default. The `GraphCanvasMenu` component is absolutely positioned
(`right-0 bottom-0`) inside the `graph-canvas-panel` SplitterPanel. On
mobile viewports, the panel's bounding box can be smaller than the full
canvas area, causing the toolbar to be clipped by the `overflow:
hidden`.

## Solution

Add `overflow-visible` to the `graph-canvas-panel` SplitterPanel class
to override PrimeVue's default `overflow: hidden`. This allows the
absolutely-positioned toolbar (and minimap) to remain visible regardless
of viewport size.

<img width="873" height="1056" alt="image"
src="https://github.com/user-attachments/assets/7239a5ce-8ce8-4e1d-a8ff-6d6d3c61f5da"
/>


┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10168-fix-make-graph-canvas-toolbar-visible-on-mobile-3266d73d36508130b675e839cb748fd5)
by [Unito](https://www.unito.io)

src/components/LiteGraphCanvasSplitterOverlay.test.ts

@@ -0,0 +1,28 @@
+import { readFileSync } from 'fs'
+import { resolve } from 'path'
+import { describe, expect, it } from 'vitest'
+
+/**
+ * Regression test: the graph-canvas-panel SplitterPanel must not clip
+ * absolutely-positioned children (like GraphCanvasMenu).
+ *
+ * PrimeVue applies `overflow: hidden` to all SplitterPanels by default.
+ * Without an explicit `overflow-visible` override, the bottom-right canvas
+ * toolbar becomes invisible on mobile viewports where the panel's bounding
+ * box is smaller than the full canvas area.
+ *
+ * @see https://www.notion.so/Bug-Graph-canvas-toolbar-not-visible-on-mobile-3246d73d36508144ae00f10065c42fac
+ */
+describe('LiteGraphCanvasSplitterOverlay', () => {
+  it('graph-canvas-panel has overflow-visible to prevent clipping toolbar on mobile', () => {
+    const filePath = resolve(__dirname, 'LiteGraphCanvasSplitterOverlay.vue')
+    const source = readFileSync(filePath, 'utf-8')
+
+    // The SplitterPanel wrapping graph-canvas-panel must include overflow-visible
+    // to override PrimeVue's default overflow:hidden on .p-splitterpanel.
+    // Without this, GraphCanvasMenu (absolute right-0 bottom-0) gets clipped on mobile.
+    expect(source).toMatch(
+      /class="[^"]*graph-canvas-panel[^"]*overflow-visible/
+    )
+  })
+})