feat(erase-object): add freeform lasso selection mode (#503)

Adds a Brush | Lasso toggle to the object eraser. Lasso lets the user drag a freeform loop that auto-closes and fills into the mask, so they select around a subject instead of painting every pixel. Frontend-only; the mask contract is unchanged. Also un-skips the erase-object e2e suite via a shared mockAiFeaturesInstalled helper (7 tests now run; 2 multi-file tests fixme'd for a pre-existing tool-page remount bug). Closes #492.

tests/e2e/helpers.ts

@@ -128,6 +128,43 @@ export async function uploadTestImage(page: Page): Promise<void> {
   await page.waitForTimeout(500);
 }
 
+// ---------------------------------------------------------------------------
+// mockAiFeaturesInstalled() — make AI-tool bundles report as installed.
+//
+// AI tools (erase-object, upscale, ...) render a FeatureInstallPrompt instead of
+// the tool UI when their bundle is missing, so their e2e specs otherwise skip in
+// CI and on any box without the bundle. Mock the feature-status endpoint so the
+// tool UI renders. Call BEFORE navigating to the tool page, then goto (a full
+// load resets the in-memory features store, which re-fetches through this mock).
+// These specs exercise client-side UI up to mask generation, not the real AI
+// backend / processing.
+// ---------------------------------------------------------------------------
+export async function mockAiFeaturesInstalled(
+  page: Page,
+  bundles: Array<{ id: string; enablesTools: string[]; name?: string }>,
+): Promise<void> {
+  await page.route("**/api/v1/features", (route) =>
+    route.fulfill({
+      status: 200,
+      contentType: "application/json",
+      body: JSON.stringify({
+        bundles: bundles.map((b) => ({
+          id: b.id,
+          name: b.name ?? b.id,
+          description: "",
+          status: "installed",
+          installedVersion: "1.0.0",
+          estimatedSize: "",
+          downloadBytes: null,
+          installedBytes: null,
+          enablesTools: b.enablesTools,
+          progress: null,
+        })),
+      }),
+    }),
+  );
+}
+
 // ---------------------------------------------------------------------------
 // waitForProcessing() — wait for processing to complete
 // ---------------------------------------------------------------------------