Story 26: Establish TDD workflow and quality gates

Add workflow engine with acceptance gates, test recording, and review
queue. Frontend displays gate status (blocked/ready), test summaries,
failing badges, and warnings. Proceed action is disabled when gates
are not met. Includes 13 unit tests (Vitest) and 9 E2E tests
(Playwright) covering all five acceptance criteria.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/api/workflow.ts

@@ -0,0 +1,101 @@
+export type TestStatus = "pass" | "fail";
+
+export interface TestCasePayload {
+	name: string;
+	status: TestStatus;
+	details?: string | null;
+}
+
+export interface RecordTestsPayload {
+	story_id: string;
+	unit: TestCasePayload[];
+	integration: TestCasePayload[];
+}
+
+export interface AcceptanceRequest {
+	story_id: string;
+}
+
+export interface TestRunSummaryResponse {
+	total: number;
+	passed: number;
+	failed: number;
+}
+
+export interface AcceptanceResponse {
+	can_accept: boolean;
+	reasons: string[];
+	warning?: string | null;
+	summary: TestRunSummaryResponse;
+	missing_categories: string[];
+}
+
+export interface ReviewStory {
+	story_id: string;
+	can_accept: boolean;
+	reasons: string[];
+	warning?: string | null;
+	summary: TestRunSummaryResponse;
+	missing_categories: string[];
+}
+
+export interface ReviewListResponse {
+	stories: ReviewStory[];
+}
+
+const DEFAULT_API_BASE = "/api";
+
+function buildApiUrl(path: string, baseUrl = DEFAULT_API_BASE): string {
+	return `${baseUrl}${path}`;
+}
+
+async function requestJson<T>(
+	path: string,
+	options: RequestInit = {},
+	baseUrl = DEFAULT_API_BASE,
+): Promise<T> {
+	const res = await fetch(buildApiUrl(path, baseUrl), {
+		headers: {
+			"Content-Type": "application/json",
+			...(options.headers ?? {}),
+		},
+		...options,
+	});
+
+	if (!res.ok) {
+		const text = await res.text();
+		throw new Error(text || `Request failed (${res.status})`);
+	}
+
+	return res.json() as Promise<T>;
+}
+
+export const workflowApi = {
+	recordTests(payload: RecordTestsPayload, baseUrl?: string) {
+		return requestJson<boolean>(
+			"/workflow/tests/record",
+			{ method: "POST", body: JSON.stringify(payload) },
+			baseUrl,
+		);
+	},
+	getAcceptance(payload: AcceptanceRequest, baseUrl?: string) {
+		return requestJson<AcceptanceResponse>(
+			"/workflow/acceptance",
+			{ method: "POST", body: JSON.stringify(payload) },
+			baseUrl,
+		);
+	},
+	getReviewQueue(baseUrl?: string) {
+		return requestJson<ReviewListResponse>("/workflow/review", {}, baseUrl);
+	},
+	getReviewQueueAll(baseUrl?: string) {
+		return requestJson<ReviewListResponse>("/workflow/review/all", {}, baseUrl);
+	},
+	ensureAcceptance(payload: AcceptanceRequest, baseUrl?: string) {
+		return requestJson<boolean>(
+			"/workflow/acceptance/ensure",
+			{ method: "POST", body: JSON.stringify(payload) },
+			baseUrl,
+		);
+	},
+};