test: add unit tests for pure logic modules

Add 22 test files covering imager, soundtracks, browser-headers, source-keys (figure/pet/effect), effect-source, plus catalog-translations, catalog-layouts, client-translation-files, translations-utils, and various admin/services/helpers modules. Total test count increases by 120+.

src/lib/json5-patch.test.ts

@@ -0,0 +1,54 @@
+import { describe, expect, it } from "vitest";
+import { patchJson5 } from "./json5-patch";
+
+const sample = `// header comment
+{
+	// a section
+	"title": "Hotel",
+	"subtitle": "Welcome!",
+	'nested.key': "keep me",
+}`;
+
+describe("patchJson5", () => {
+	it("surgically replaces a value while preserving comments", () => {
+		const result = patchJson5(sample, { title: "Hotel" }, { title: "Resort" });
+		expect(result.unpatchedKeys).toEqual([]);
+		expect(result.content).toContain('"title": "Resort"');
+		expect(result.content).toContain("// a section");
+		expect(result.content).toContain('"subtitle": "Welcome!"');
+	});
+
+	it("does not touch keys whose value is unchanged", () => {
+		const result = patchJson5(sample, { title: "Hotel" }, { title: "Hotel" });
+		expect(result.unpatchedKeys).toEqual([]);
+		expect(result.content).toBe(sample);
+	});
+
+	it("reports keys missing from the original", () => {
+		const result = patchJson5(sample, { title: "Hotel" }, { newKey: "x" });
+		expect(result.unpatchedKeys).toEqual(["newKey"]);
+		expect(result.content).toBe(sample);
+	});
+
+	it("reports keys that cannot be located in the source", () => {
+		const result = patchJson5(sample, { title: "Hotel" }, { title: "nope" });
+		// "title" is present and findable, so it patches.
+		expect(result.unpatchedKeys).toEqual([]);
+		expect(result.content).toContain('"title": "nope"');
+	});
+
+	it("handles single-quoted keys and escaped values", () => {
+		const result = patchJson5(
+			sample,
+			{ "nested.key": "keep me" },
+			{ "nested.key": 'say "hi"' },
+		);
+		expect(result.unpatchedKeys).toEqual([]);
+		expect(result.content).toContain(`'nested.key': "say \\"hi\\""`);
+	});
+
+	it("reports keys that do not appear in the file at all", () => {
+		const result = patchJson5(sample, { missing: "a" }, { missing: "b" });
+		expect(result.unpatchedKeys).toEqual(["missing"]);
+	});
+});