refactor: extract DefaultGraphPositions constants from ComfyPage.ts

- Create browser_tests/fixtures/constants/defaultGraphPositions.ts with all hardcoded default graph positions

- Create browser_tests/fixtures/constants/types.ts with Position and Size interfaces

- Update ComfyPage.ts to import and use DefaultGraphPositions

- Reduces duplication and prepares for further modular extraction

Amp-Thread-ID: https://ampcode.com/threads/T-019c1201-adec-7363-96d5-446d0a98e4cf
Co-authored-by: Amp <amp@ampcode.com>

browser_tests/fixtures/constants/defaultGraphPositions.ts

@@ -0,0 +1,53 @@
+import type { Position } from './types'
+
+/**
+ * Hardcoded positions for the default graph loaded in tests.
+ * These coordinates are specific to the default workflow viewport.
+ */
+export const DefaultGraphPositions = {
+  // Node click positions
+  textEncodeNode1: { x: 618, y: 191 },
+  textEncodeNode2: { x: 622, y: 400 },
+  textEncodeNodeToggler: { x: 430, y: 171 },
+  emptySpaceClick: { x: 35, y: 31 },
+
+  // Slot positions
+  clipTextEncodeNode1InputSlot: { x: 427, y: 198 },
+  clipTextEncodeNode2InputSlot: { x: 422, y: 402 },
+  clipTextEncodeNode2InputLinkPath: { x: 395, y: 422 },
+  loadCheckpointNodeClipOutputSlot: { x: 332, y: 509 },
+  emptySpace: { x: 427, y: 98 },
+
+  // Widget positions
+  emptyLatentWidgetClick: { x: 724, y: 645 },
+
+  // Node positions and sizes for resize operations
+  ksampler: {
+    pos: { x: 863, y: 156 },
+    size: { width: 315, height: 292 }
+  },
+  loadCheckpoint: {
+    pos: { x: 26, y: 444 },
+    size: { width: 315, height: 127 }
+  },
+  emptyLatent: {
+    pos: { x: 473, y: 579 },
+    size: { width: 315, height: 136 }
+  }
+} as const satisfies {
+  textEncodeNode1: Position
+  textEncodeNode2: Position
+  textEncodeNodeToggler: Position
+  emptySpaceClick: Position
+  clipTextEncodeNode1InputSlot: Position
+  clipTextEncodeNode2InputSlot: Position
+  clipTextEncodeNode2InputLinkPath: Position
+  loadCheckpointNodeClipOutputSlot: Position
+  emptySpace: Position
+  emptyLatentWidgetClick: Position
+  ksampler: { pos: Position; size: { width: number; height: number } }
+  loadCheckpoint: { pos: Position; size: { width: number; height: number } }
+  emptyLatent: { pos: Position; size: { width: number; height: number } }
+}
+
+export type DefaultGraphPositionsType = typeof DefaultGraphPositions