fix: cache ctx.measureText results to avoid redundant calls in draw loop (#9404)

## What
Add a per-frame text measurement cache for all hot-path
ctx.measureText() calls.

## Why
drawTruncatingText() in BaseWidget calls ctx.measureText() per widget
per frame with zero caching. For a 50-node workflow at 60fps:
~78,000-243,000 measureText calls/sec. Text labels rarely change between
frames.

## How
Global Map<string, number> cache keyed by font+text, cleared once per
frame at the start of drawFrontCanvas(). Replaces direct
ctx.measureText() calls in BaseWidget.drawTruncatingText, draw.ts
truncateTextToWidth/drawTextInArea, LGraphBadge.getWidth,
LGraphButton.getWidth, and textUtils.truncateText.

## Perf Impact
Expected: ~95% reduction in measureText calls (only cache misses on
first frame and value changes). Firefox has slower measureText than
Chrome, so this disproportionately benefits Firefox.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9404-fix-cache-ctx-measureText-results-to-avoid-redundant-calls-in-draw-loop-31a6d73d3650814e9cdac16949c55cb7)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>

src/lib/litegraph/src/LGraphNode.ts

@@ -17,6 +17,7 @@ import {
 } from '@/lib/litegraph/src/utils/type'
 
 import { SUBGRAPH_OUTPUT_ID } from '@/lib/litegraph/src/constants'
+import { cachedMeasureText } from '@/lib/litegraph/src/utils/textMeasureCache'
 import type { DragAndScale } from './DragAndScale'
 import type { LGraph } from './LGraph'
 import { BadgePosition, LGraphBadge } from './LGraphBadge'
@@ -2083,7 +2084,7 @@ export class LGraphNode
       this._collapsed_width = Math.min(
         this.size[0],
         ctx
-          ? ctx.measureText(this.getTitle() ?? '').width +
+          ? cachedMeasureText(ctx, this.getTitle() ?? '') +
               LiteGraph.NODE_TITLE_HEIGHT * 2
           : 0
       )