WIP: Batch 3 — backfill frontend tests

- usePathCompletion: 16 tests (isFuzzyMatch, getCurrentPartial, hook behavior)
- api/client.ts: 9 tests (fetch mocks for all major endpoints, error handling)
- api/workflow.ts: 6 tests (record, acceptance, review queue, ensure)

Frontend tests: 13 → 44

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

frontend/src/components/selection/usePathCompletion.test.ts

@@ -0,0 +1,160 @@
+import { act, renderHook, waitFor } from "@testing-library/react";
+import { describe, expect, it, vi } from "vitest";
+import type { FileEntry } from "./usePathCompletion";
+import {
+	getCurrentPartial,
+	isFuzzyMatch,
+	usePathCompletion,
+} from "./usePathCompletion";
+
+describe("isFuzzyMatch", () => {
+	it("matches when query is empty", () => {
+		expect(isFuzzyMatch("anything", "")).toBe(true);
+	});
+
+	it("matches exact prefix", () => {
+		expect(isFuzzyMatch("Documents", "Doc")).toBe(true);
+	});
+
+	it("matches fuzzy subsequence", () => {
+		expect(isFuzzyMatch("Documents", "dms")).toBe(true);
+	});
+
+	it("is case insensitive", () => {
+		expect(isFuzzyMatch("Documents", "DOCU")).toBe(true);
+	});
+
+	it("rejects when chars not found in order", () => {
+		expect(isFuzzyMatch("abc", "acb")).toBe(false);
+	});
+
+	it("rejects completely unrelated", () => {
+		expect(isFuzzyMatch("hello", "xyz")).toBe(false);
+	});
+});
+
+describe("getCurrentPartial", () => {
+	it("returns empty for empty input", () => {
+		expect(getCurrentPartial("")).toBe("");
+	});
+
+	it("returns empty when input ends with slash", () => {
+		expect(getCurrentPartial("/home/user/")).toBe("");
+	});
+
+	it("returns last segment", () => {
+		expect(getCurrentPartial("/home/user/Doc")).toBe("Doc");
+	});
+
+	it("returns full input when no slash", () => {
+		expect(getCurrentPartial("Doc")).toBe("Doc");
+	});
+
+	it("trims then evaluates: trailing-slash input returns empty", () => {
+		// "  /home/user/  " trims to "/home/user/" which ends with slash
+		expect(getCurrentPartial("  /home/user/  ")).toBe("");
+	});
+
+	it("trims then returns last segment", () => {
+		expect(getCurrentPartial("  /home/user/Doc  ")).toBe("Doc");
+	});
+});
+
+describe("usePathCompletion hook", () => {
+	const mockListDir = vi.fn<(path: string) => Promise<FileEntry[]>>();
+
+	beforeEach(() => {
+		mockListDir.mockReset();
+	});
+
+	it("returns empty matchList for empty input", async () => {
+		const { result } = renderHook(() =>
+			usePathCompletion({
+				pathInput: "",
+				setPathInput: vi.fn(),
+				homeDir: "/home/user",
+				listDirectoryAbsolute: mockListDir,
+				debounceMs: 0,
+			}),
+		);
+
+		// Allow effect + setTimeout(0) to fire
+		await waitFor(() => {
+			expect(mockListDir).not.toHaveBeenCalled();
+		});
+
+		expect(result.current.matchList).toEqual([]);
+	});
+
+	it("fetches directory listing and returns matches", async () => {
+		mockListDir.mockResolvedValue([
+			{ name: "Documents", kind: "dir" },
+			{ name: "Downloads", kind: "dir" },
+			{ name: ".bashrc", kind: "file" },
+		]);
+
+		const { result } = renderHook(() =>
+			usePathCompletion({
+				pathInput: "/home/user/",
+				setPathInput: vi.fn(),
+				homeDir: "/home/user",
+				listDirectoryAbsolute: mockListDir,
+				debounceMs: 0,
+			}),
+		);
+
+		await waitFor(() => {
+			expect(result.current.matchList.length).toBe(2);
+		});
+
+		expect(result.current.matchList[0].name).toBe("Documents");
+		expect(result.current.matchList[1].name).toBe("Downloads");
+		expect(result.current.matchList.every((m) => m.path.endsWith("/"))).toBe(
+			true,
+		);
+	});
+
+	it("filters by fuzzy match on partial input", async () => {
+		mockListDir.mockResolvedValue([
+			{ name: "Documents", kind: "dir" },
+			{ name: "Downloads", kind: "dir" },
+			{ name: "Desktop", kind: "dir" },
+		]);
+
+		const { result } = renderHook(() =>
+			usePathCompletion({
+				pathInput: "/home/user/Doc",
+				setPathInput: vi.fn(),
+				homeDir: "/home/user",
+				listDirectoryAbsolute: mockListDir,
+				debounceMs: 0,
+			}),
+		);
+
+		await waitFor(() => {
+			expect(result.current.matchList.length).toBe(1);
+		});
+
+		expect(result.current.matchList[0].name).toBe("Documents");
+	});
+
+	it("calls setPathInput when acceptMatch is invoked", () => {
+		const setPathInput = vi.fn();
+
+		const { result } = renderHook(() =>
+			usePathCompletion({
+				pathInput: "/home/",
+				setPathInput,
+				homeDir: "/home",
+				listDirectoryAbsolute: mockListDir,
+				debounceMs: 0,
+			}),
+		);
+
+		act(() => {
+			result.current.acceptMatch("/home/user/Documents/");
+		});
+
+		expect(setPathInput).toHaveBeenCalledWith("/home/user/Documents/");
+	});
+});

frontend/src/components/selection/usePathCompletion.ts

@@ -30,7 +30,7 @@ export interface UsePathCompletionResult {
 	closeSuggestions: () => void;
 }
 
-function isFuzzyMatch(candidate: string, query: string) {
+export function isFuzzyMatch(candidate: string, query: string) {
 	if (!query) return true;
 	const lowerCandidate = candidate.toLowerCase();
 	const lowerQuery = query.toLowerCase();
@@ -43,7 +43,7 @@ function isFuzzyMatch(candidate: string, query: string) {
 	return true;
 }
 
-function getCurrentPartial(input: string) {
+export function getCurrentPartial(input: string) {
 	const trimmed = input.trim();
 	if (!trimmed) return "";
 	if (trimmed.endsWith("/")) return "";