test: expand test coverage across all layers (+1,157 tests)

Fix 2 failing unit tests (landing hero text mismatch) and broken
coverage tooling (brace-expansion v5 override breaking minimatch).
Add ~1,097 new test cases via 14-agent parallel expansion:

- Unit: +290 tests (AI bridge, image-engine, stores, API helpers)
- Integration: +504 tests (all tools, cross-format matrix, adversarial)
- E2E: +363 tests (navigation, tool UI, batch/pipeline, settings,
  visual regression, accessibility, performance, cross-browser)

Total: 4,223 unit + 6,057 integration + 1,563 E2E = 11,843 tests

tests/e2e/gui-tools-overlay.spec.ts

@@ -721,7 +721,7 @@ test.describe("GUI Watermark & Overlay Tools", () => {
       // The image wrapper should have styling applied (border, padding, etc.)
       // Check that some wrapper element has a non-default style
       const wrapper = previewImg.locator("..");
-      const bgColor = await wrapper.evaluate((el) => window.getComputedStyle(el).backgroundColor);
+      const _bgColor = await wrapper.evaluate((el) => window.getComputedStyle(el).backgroundColor);
       // Polaroid preset uses white background -- just verify the preview didn't error
       await expect(previewImg).toBeVisible();
     });