Extend element registry and migrate all tests to semantic selectors

Phase 2 of element registry migration - eliminate hardcoded coordinates:

Element tracker additions:
- wxTreeCtrl items (clickTreeItem, findTreeItem)
- wxDataViewCtrl items and column headers
- wxPropertyGrid rows
- wxListBox items
- wxSpinButton arrows
- wxSlider thumb/track
- wxTextCtrl area
- wxSearchCtrl field
- wxAuiManager pane content areas
- wxCalendarCtrl dates

Test migrations:
- 24 test files updated to use element registry helpers
- Replaced coordinate-based clicks with semantic selectors
- Added find-hardcoded-coords.sh script for auditing

Remaining coordinates are legitimate (scroll positioning, drawing, test.fail blocks).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/e2e/collapsible.spec.ts

@@ -1,5 +1,6 @@
 // wxCollapsiblePane Tests - Collapsible sections for property panels
 import { test, expect, tryLoadApp } from './utils/fixtures';
+import { clickByLabel } from './utils/element-tracker';
 
 test.describe('wxCollapsiblePane Tests', () => {
 
@@ -55,15 +56,9 @@ test.describe('wxCollapsiblePane Tests', () => {
       return;
     }
 
-    const canvas = page.locator('#canvas');
-    const box = await canvas.boundingBox();
-    if (!box) {
-      test.skip();
-      return;
-    }
-
-    // Click Expand All button (approximate position)
-    await page.mouse.click(box.x + 150, box.y + 100);
+    // Click Expand All button using element registry
+    const clicked = await clickByLabel(page, 'Expand All');
+    expect(clicked, 'Expand All button should be found and clicked').toBe(true);
     await page.waitForTimeout(300);
 
     await page.screenshot({ path: 'test-results/collapsible-04-expand-all.png', fullPage: true });
@@ -82,15 +77,9 @@ test.describe('wxCollapsiblePane Tests', () => {
       return;
     }
 
-    const canvas = page.locator('#canvas');
-    const box = await canvas.boundingBox();
-    if (!box) {
-      test.skip();
-      return;
-    }
-
-    // Click Collapse All button (approximate position, second button)
-    await page.mouse.click(box.x + 300, box.y + 100);
+    // Click Collapse All button using element registry
+    const clicked = await clickByLabel(page, 'Collapse All');
+    expect(clicked, 'Collapse All button should be found and clicked').toBe(true);
     await page.waitForTimeout(300);
 
     await page.screenshot({ path: 'test-results/collapsible-05-collapse-all.png', fullPage: true });