test: expand test coverage across unit, integration, e2e, and e2e-docker suites

Add ~210 new tests filling gaps identified by a comprehensive 14-agent
coverage audit. Unit+integration tests go from 9,388 to 9,484 (all passing).

Unit tests (+36):
- AI bridge: OOM fallback path, custom tier option
- Web lib: api-errors, format date/datetime, tool-i18n coverage

Integration tests (+19):
- Format matrix: ai-canvas-expand and find-duplicates added to cross-format matrix
- Adversarial: SVG XXE attacks, SQL injection in settings, request body size
  limits, race conditions with identical filenames

E2E Docker (+3):
- ai-canvas-expand tool coverage with HEIC input and edge cases

E2E GUI (~150+):
- Navigation: login rate limiting, ai-canvas-expand in parameterized list
- Responsive: dropzone visibility, text readability, dialog bounds at all viewports
- Keyboard: shortcuts verified from automate, files, tool, and fullscreen pages
- Tool UI: undo/state-reset for 16 tools, crop canvas drag handles, rotate/border
  live preview, linked aspect-ratio inputs for resize
- Batch: per-image undo isolation, batch compress/convert/rotate (not just resize)
- Pipeline: tool palette search, step collapse/expand visibility
- Settings: audit log entry verification, system settings persistence, teams CRUD,
  role permission toggling
- RBAC: user/editor 403 on roles/teams endpoints, privilege escalation prevention,
  cross-role tab parity documented as intentional
- Accessibility: skip-to-content link (WCAG 2.4.1), comprehensive color contrast
  for all headings/body/buttons in both themes with DOM-walking background detection
- Resilience: auth expiry 401 redirect, rate limit 429 handling
- Performance: JS heap memory stability for tool navigation, dialog cycling,
  upload/clear cycles, rapid page navigation

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

@@ -248,4 +248,73 @@ test.describe("GUI Metadata Tools", () => {
       await expect(submitBtn).toBeEnabled();
     });
   });
+
+  // ========================================================================
+  // UNDO / STATE RESET (Metadata tools)
+  // ========================================================================
+  test.describe("Undo and State Reset", () => {
+    test("strip-metadata: undo after processing returns to settings", async ({
+      loggedInPage: page,
+    }) => {
+      await page.goto("/strip-metadata");
+      await uploadTestImage(page);
+
+      await page.getByTestId("strip-metadata-submit").click();
+      await waitForProcessing(page);
+
+      await expect(page.getByTestId("strip-metadata-download")).toBeVisible({ timeout: 15_000 });
+
+      await page.getByRole("button", { name: /undo/i }).click();
+
+      await expect(page.getByTestId("strip-metadata-submit")).toBeVisible({ timeout: 5_000 });
+      await expect(page.getByTestId("strip-metadata-download")).not.toBeVisible();
+      // Settings should still be visible
+      await expect(page.getByText("Remove All Metadata")).toBeVisible();
+    });
+
+    test("edit-metadata: undo after processing returns to form", async ({ loggedInPage: page }) => {
+      await page.goto("/edit-metadata");
+      await uploadTestImage(page);
+      await page.waitForSelector('[id="em-artist"]', { timeout: 10_000 });
+
+      await page.fill('[id="em-artist"]', "Undo Test Artist");
+      await page.getByTestId("edit-metadata-submit").click();
+      await waitForProcessing(page);
+
+      await expect(page.getByTestId("edit-metadata-download")).toBeVisible({ timeout: 15_000 });
+
+      await page.getByRole("button", { name: /undo/i }).click();
+
+      await expect(page.getByTestId("edit-metadata-submit")).toBeVisible({ timeout: 5_000 });
+      await expect(page.getByTestId("edit-metadata-download")).not.toBeVisible();
+    });
+
+    test("strip-metadata: clear all returns to dropzone", async ({ loggedInPage: page }) => {
+      await page.goto("/strip-metadata");
+      await uploadTestImage(page);
+
+      await expect(page.getByText("Remove All Metadata")).toBeVisible();
+
+      await page.getByText("Clear all").click();
+
+      await expect(page.getByText("Upload from computer")).toBeVisible({ timeout: 5_000 });
+    });
+
+    test("navigate away from info tool resets state", async ({ loggedInPage: page }) => {
+      await page.goto("/info");
+      await uploadTestImage(page);
+
+      await page.getByTestId("info-submit").click();
+      await waitForProcessing(page);
+
+      await expect(page.getByText("Dimensions").first()).toBeVisible({ timeout: 15_000 });
+
+      // Navigate away and back
+      await page.goto("/resize");
+      await page.goto("/info");
+
+      // Should be back at dropzone
+      await expect(page.getByText("Upload from computer")).toBeVisible();
+    });
+  });
 });