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-layer-effects.spec.ts

@@ -0,0 +1,131 @@
+import { createNewDocument, drawOnCanvas, expect, selectTool, test } from "./helpers";
+
+test.describe("Editor Layer Effects and Blend Modes", () => {
+  test.beforeEach(async ({ editorPage: page }) => {
+    await createNewDocument(page);
+    // Ensure layers tab is active
+    await page.locator("[data-testid='tab-layers']").click();
+    await page.waitForTimeout(300);
+  });
+
+  test("blend mode dropdown exists in layers panel", async ({ editorPage: page }) => {
+    const blendSelect = page.locator("[data-testid='blend-mode-select']");
+    await expect(blendSelect).toBeVisible();
+
+    // Should default to Normal (source-over)
+    await expect(blendSelect).toHaveValue("source-over");
+  });
+
+  test("blend mode can be changed", async ({ editorPage: page }) => {
+    const blendSelect = page.locator("[data-testid='blend-mode-select']");
+    await expect(blendSelect).toBeVisible();
+
+    // Change to Multiply
+    await blendSelect.selectOption("multiply");
+    await page.waitForTimeout(300);
+
+    await expect(blendSelect).toHaveValue("multiply");
+
+    // Change to Screen
+    await blendSelect.selectOption("screen");
+    await page.waitForTimeout(300);
+
+    await expect(blendSelect).toHaveValue("screen");
+
+    // Change to Overlay
+    await blendSelect.selectOption("overlay");
+    await page.waitForTimeout(300);
+
+    await expect(blendSelect).toHaveValue("overlay");
+  });
+
+  test("effects section exists (drop shadow, stroke)", async ({ editorPage: page }) => {
+    test.slow();
+
+    // We need a selected object for the effects section to appear.
+    // Draw something on the canvas to create an object.
+    await selectTool(page, "shape-rect");
+    await drawOnCanvas(page, 100, 100, 300, 250);
+    await page.waitForTimeout(500);
+
+    // Switch to move tool and click the shape to select it
+    await selectTool(page, "move");
+    const canvas = page.locator("canvas").first();
+    const box = await canvas.boundingBox();
+    if (!box) throw new Error("Canvas not found");
+    await page.mouse.click(box.x + 200, box.y + 175);
+    await page.waitForTimeout(300);
+
+    // Switch to layers tab to see effects
+    await page.locator("[data-testid='tab-layers']").click();
+    await page.waitForTimeout(300);
+
+    // The Layer Effects section should be visible
+    const effectsLabel = page.getByText("Layer Effects");
+    await expect(effectsLabel).toBeVisible();
+
+    // Drop Shadow and Stroke labels should exist
+    await expect(page.getByText("Drop Shadow").first()).toBeVisible();
+    await expect(page.getByText("Stroke").first()).toBeVisible();
+  });
+
+  test("drop shadow toggle enables shadow settings", async ({ editorPage: page }) => {
+    test.slow();
+
+    // Create and select a shape object
+    await selectTool(page, "shape-rect");
+    await drawOnCanvas(page, 100, 100, 300, 250);
+    await page.waitForTimeout(500);
+
+    await selectTool(page, "move");
+    const canvas = page.locator("canvas").first();
+    const box = await canvas.boundingBox();
+    if (!box) throw new Error("Canvas not found");
+    await page.mouse.click(box.x + 200, box.y + 175);
+    await page.waitForTimeout(300);
+
+    await page.locator("[data-testid='tab-layers']").click();
+    await page.waitForTimeout(300);
+
+    // Find the Drop Shadow checkbox
+    const dropShadowLabel = page.locator("label").filter({ hasText: "Drop Shadow" });
+    const dropShadowCheckbox = dropShadowLabel.locator("input[type='checkbox']");
+    await dropShadowCheckbox.scrollIntoViewIfNeeded();
+
+    // Initially unchecked
+    await expect(dropShadowCheckbox).not.toBeChecked();
+
+    // Enable drop shadow
+    await dropShadowCheckbox.check();
+    await page.waitForTimeout(300);
+
+    await expect(dropShadowCheckbox).toBeChecked();
+
+    // Expand the section to see controls by clicking the chevron
+    const expandBtn = dropShadowLabel.locator("..").locator("button[aria-label*='Expand']");
+    if (await expandBtn.isVisible()) {
+      await expandBtn.click();
+      await page.waitForTimeout(300);
+    }
+  });
+
+  test("layer opacity slider works", async ({ editorPage: page }) => {
+    const slider = page.locator("[data-testid='layer-opacity-slider']");
+    await expect(slider).toBeVisible();
+
+    // Default opacity should be 100 (full)
+    await expect(slider).toHaveValue("100");
+
+    // Change opacity to 50
+    await slider.fill("50");
+    await page.waitForTimeout(300);
+
+    await expect(slider).toHaveValue("50");
+
+    // Change back to 75
+    await slider.fill("75");
+    await page.waitForTimeout(300);
+
+    await expect(slider).toHaveValue("75");
+  });
+});