Fix oxlint --deny-warnings and eliminate all biome-ignores

--deny warnings was a no-op (not a valid category); the correct flag
is --deny-warnings. Fixed all 8 pre-existing warnings and removed
every biome-ignore from source and test files. Simplified the check
script to zero-tolerance: any biome-ignore now fails the build.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/src/components/__tests__/source-manager.test.tsx

@@ -28,7 +28,7 @@ beforeAll(() => {
 
 afterEach(cleanup);
 
-function renderWithSources(sources: CachedSourceInfo[] = []) {
+function renderWithSources(sources: CachedSourceInfo[] = []): void {
 	const adapters = createTestAdapters();
 	// Wire getCachedSources to return the provided sources initially,
 	// then empty after clear operations
@@ -57,14 +57,14 @@ function renderWithSources(sources: CachedSourceInfo[] = []) {
 
 describe("SourceManager", () => {
 	it("shows 'No cached sources' empty state when no sources", async () => {
-		void renderWithSources([]);
+		renderWithSources([]);
 		await waitFor(() => {
 			expect(screen.getByText("No cached sources")).toBeInTheDocument();
 		});
 	});
 
 	it("lists cached sources with display name and creature count", async () => {
-		void renderWithSources([
+		renderWithSources([
 			{
 				sourceCode: "mm",
 				displayName: "Monster Manual",
@@ -88,7 +88,7 @@ describe("SourceManager", () => {
 
 	it("Clear All button removes all sources", async () => {
 		const user = userEvent.setup();
-		void renderWithSources([
+		renderWithSources([
 			{
 				sourceCode: "mm",
 				displayName: "Monster Manual",
@@ -110,7 +110,7 @@ describe("SourceManager", () => {
 
 	it("individual source delete button removes that source", async () => {
 		const user = userEvent.setup();
-		void renderWithSources([
+		renderWithSources([
 			{
 				sourceCode: "mm",
 				displayName: "Monster Manual",