fix: resolve 41 bugs and wire 21 unimplemented features in image editor

Canvas rendering:
- Fix Konva filter application order (filters before cache)
- Implement 6 missing filters (motionBlur, radialBlur, surfaceBlur, vignette, grain, sharpen)
- Implement exposure, vibrance, warmth adjustments as custom Konva filters
- Apply layer blend modes via globalCompositeOperation
- Apply object effects (drop shadow, outer glow, stroke) to all shapes
- Mount SmartGuidesOverlay during move tool drag
- Clip pixel grid to visible viewport (200-line cap for performance)

Store logic:
- resizeImage now scales all objects proportionally (points, radii, fontSize)
- rotate/flip/trim handle line/arrow points arrays and center-based objects
- applyCrop creates cropped source image via offscreen canvas
- invertSelection creates mask from bounds when no mask exists
- cutObjects uses single atomic set() to prevent race conditions
- sendToBack respects layer ordering in multi-layer documents
- Add batchNudge() and commitHistory() for undoable nudge operations
- Add updateLayerThumbnail() method

Tool hooks:
- Fix clone stamp/dodge/burn perf (toDataURL only on mouseUp, not every move)
- Fix magic wand zoom/pixelRatio with explicit stage.toCanvas() viewport
- Fix eyedropper sampling with unzoomed canvas export
- Fix selection tool stale closure via isDrawingRef
- Implement polygonal lasso (click-to-place vertices, double-click to close)
- Implement selection subtract mode (geometric and mask-based)
- Implement gradient live preview during drag
- Fix transform/move tool to persist changes and handle ellipse/polygon/star

UI wiring:
- Mount rulers and guidelines in editor page
- Wire histogram with live canvas imageData
- Wire autosave recovery with blob-to-dataURL conversion
- Wire fill dialog to Shift+Backspace shortcut
- Wire eyedropper and transform options to options bar
- Fix history panel undo/redo button reactive state via useSyncExternalStore
- Fix layer row name click to select layer (timer-based click/dblclick)
- Fix zoom animation coordinate drift with progressive store sync
- Fix copy merged to use Konva stage composite export

Tests:
- 49 new unit tests (store fixes + konva filters)
- 8 new E2E test files with 39 test cases

tests/e2e-editor/editor-rulers-guides.spec.ts

@@ -0,0 +1,73 @@
+import { createNewDocument, expect, test } from "./helpers";
+
+test.describe("Editor Rulers and Guides", () => {
+  test.beforeEach(async ({ editorPage: page }) => {
+    await createNewDocument(page);
+  });
+
+  test("rulers are hidden by default", async ({ editorPage: page }) => {
+    // The ruler canvases render only when rulersVisible is true.
+    // By default rulers are hidden, so the ruler-specific canvases
+    // (with cursor-col-resize / cursor-row-resize) should not be present.
+    const horizontalRuler = page.locator("canvas.cursor-col-resize");
+    const verticalRuler = page.locator("canvas.cursor-row-resize");
+
+    await expect(horizontalRuler).toHaveCount(0);
+    await expect(verticalRuler).toHaveCount(0);
+  });
+
+  test("Ctrl+R toggles ruler visibility", async ({ editorPage: page }) => {
+    // Initially hidden
+    const horizontalRuler = page.locator("canvas.cursor-col-resize");
+    await expect(horizontalRuler).toHaveCount(0);
+
+    // Press Ctrl+R to show rulers
+    await page.keyboard.press("Control+r");
+    await page.waitForTimeout(500);
+
+    // Now they should appear
+    await expect(page.locator("canvas.cursor-col-resize")).toBeVisible();
+    await expect(page.locator("canvas.cursor-row-resize")).toBeVisible();
+
+    // Press Ctrl+R again to hide
+    await page.keyboard.press("Control+r");
+    await page.waitForTimeout(500);
+
+    await expect(page.locator("canvas.cursor-col-resize")).toHaveCount(0);
+    await expect(page.locator("canvas.cursor-row-resize")).toHaveCount(0);
+  });
+
+  test("horizontal ruler appears at top edge", async ({ editorPage: page }) => {
+    // Enable rulers
+    await page.keyboard.press("Control+r");
+    await page.waitForTimeout(500);
+
+    const horizontalRuler = page.locator("canvas.cursor-col-resize");
+    await expect(horizontalRuler).toBeVisible();
+
+    // Ruler should have a fixed height of 20px (RULER_SIZE)
+    const box = await horizontalRuler.boundingBox();
+    expect(box).not.toBeNull();
+    expect(box!.height).toBe(20);
+
+    // Ruler should stretch to full width (w-full class)
+    expect(box!.width).toBeGreaterThan(100);
+  });
+
+  test("vertical ruler appears at left edge", async ({ editorPage: page }) => {
+    // Enable rulers
+    await page.keyboard.press("Control+r");
+    await page.waitForTimeout(500);
+
+    const verticalRuler = page.locator("canvas.cursor-row-resize");
+    await expect(verticalRuler).toBeVisible();
+
+    // Ruler should have a fixed width of 20px (RULER_SIZE)
+    const box = await verticalRuler.boundingBox();
+    expect(box).not.toBeNull();
+    expect(box!.width).toBe(20);
+
+    // Ruler should stretch to fill the available height
+    expect(box!.height).toBeGreaterThan(100);
+  });
+});