feat: proxy POST /model/unload endpoint

- Add unloadModel() to whisper.ts: POSTs to /model/unload with 10s
  timeout, returns parsed JSON body, throws on non-ok response
- Create src/routes/api/model/unload/+server.ts: thin POST proxy,
  passes whisper's response through, returns 502 if whisper unreachable
- Add 3 unloadModel tests (success, WHISPER_URL config, error propagation)
  — 147/147 passing

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/lib/server/whisper.ts

@@ -127,6 +127,17 @@ export async function submitJob(
 	throw new Error(`Whisper model did not become ready after ${maxAttempts} attempts`);
 }
 
+/** Unload the model from VRAM. Throws if the whisper server returns non-ok. */
+export async function unloadModel(): Promise<{ ok: boolean }> {
+	const { default: fetch } = await import('node-fetch');
+	const res = await fetch(`${whisperUrl()}/model/unload`, {
+		method: 'POST',
+		signal: AbortSignal.timeout(10000)
+	});
+	if (!res.ok) throw new Error(`/model/unload returned ${res.status}`);
+	return res.json() as Promise<{ ok: boolean }>;
+}
+
 /**
  * Cancel a queued or running job on the whisper server (best-effort).
  * Errors are silently ignored — local job status is already set to cancelled.

src/routes/api/model/unload/+server.ts

@@ -0,0 +1,13 @@
+import { json } from '@sveltejs/kit';
+import { unloadModel } from '$lib/server/whisper.js';
+
+/** Proxy for POST /model/unload on the whisper backend. */
+export async function POST() {
+	try {
+		const body = await unloadModel();
+		return json(body);
+	} catch (err: unknown) {
+		const message = err instanceof Error ? err.message : String(err);
+		return json({ ok: false, error: message }, { status: 502 });
+	}
+}

src/tests/whisper.test.ts

@@ -21,7 +21,7 @@ vi.mock('form-data', () => ({
 
 vi.mock('fs', () => ({ createReadStream: vi.fn(() => 'STREAM_PLACEHOLDER') }));
 
-import { submitJob, streamJob, getModelStatus, cancelJob } from '$lib/server/whisper.js';
+import { submitJob, streamJob, getModelStatus, cancelJob, unloadModel } from '$lib/server/whisper.js';
 
 afterEach(() => vi.clearAllMocks());
 
@@ -341,6 +341,42 @@ describe('submitJob — SSE-triggered retry', () => {
 	});
 });
 
+// ── unloadModel ───────────────────────────────────────────────────────────────
+
+describe('unloadModel', () => {
+	it('POSTs to /model/unload and returns parsed body', async () => {
+		mocks.fetch.mockResolvedValue({
+			ok: true,
+			json: () => Promise.resolve({ ok: true })
+		});
+		const result = await unloadModel();
+		expect(result).toEqual({ ok: true });
+		expect(mocks.fetch).toHaveBeenCalledWith(
+			expect.stringContaining('/model/unload'),
+			expect.objectContaining({ method: 'POST' })
+		);
+	});
+
+	it('uses the configured WHISPER_URL', async () => {
+		vi.stubEnv('WHISPER_URL', 'http://gpu-box:9090');
+		mocks.fetch.mockResolvedValue({
+			ok: true,
+			json: () => Promise.resolve({ ok: true })
+		});
+		await unloadModel();
+		expect(mocks.fetch).toHaveBeenCalledWith(
+			'http://gpu-box:9090/model/unload',
+			expect.anything()
+		);
+		vi.unstubAllEnvs();
+	});
+
+	it('throws when whisper returns a non-ok response', async () => {
+		mocks.fetch.mockResolvedValue({ ok: false, status: 409 });
+		await expect(unloadModel()).rejects.toThrow('/model/unload');
+	});
+});
+
 // ── cancelJob ─────────────────────────────────────────────────────────────────
 
 describe('cancelJob', () => {