fix: show Laya model download progress and surface errors in Settings (#12)

Track download progress in layaService (bytes/total, phase, error
state) and expose it through the laya status route. Render a progress
bar during model download in Settings via a layaStatusPresentation
service, and display download/status errors inline instead of failing
silently. Cover progress tracking and status presentation with tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

test/layaService.test.js

@@ -20,6 +20,77 @@ test('status reports an unavailable runtime without throwing', async () => {
     const status = await service.status();
     assert.equal(status.runtimeAvailable, false);
     assert.equal(status.modelPresent, false);
+    assert.equal(status.phase, 'idle');
+    assert.equal(status.downloading, false);
+    assert.equal(status.progressPercent, null);
+    assert.equal(status.bytesDownloaded, null);
+    assert.equal(status.totalBytes, null);
+    assert.equal(status.sizeBytes, 0);
+    assert.equal(status.error, null);
+});
+
+test('model download exposes an indeterminate transition and finishes ready', async () => {
+    const modelDir = await fs.mkdtemp(path.join(os.tmpdir(), 'nodecast-laya-download-'));
+    let finishDownload;
+    const downloadResponse = new Promise(resolve => { finishDownload = resolve; });
+    const service = new LayaService({
+        modelDir,
+        cache: null,
+        progressIntervalMs: 5,
+        fetch: async url => {
+            if (url.endsWith('/health')) return { ok: true, json: async () => ({ status: 'ok' }) };
+            await downloadResponse;
+            return { ok: true, json: async () => ({ answers: {} }) };
+        }
+    });
+
+    const started = service.startModelDownload();
+    assert.equal(started.phase, 'preparing');
+    assert.equal(started.downloading, true);
+    assert.equal(started.progressPercent, null);
+
+    await fs.writeFile(path.join(modelDir, 'partial.bin'), 'partial model');
+    await new Promise(resolve => setTimeout(resolve, 15));
+    const downloading = await service.status();
+    assert.equal(downloading.phase, 'downloading');
+    assert.equal(downloading.downloading, true);
+    assert.ok(downloading.bytesDownloaded > 0);
+
+    finishDownload();
+    await service.downloadPromise;
+    const ready = await service.status();
+    assert.equal(ready.phase, 'ready');
+    assert.equal(ready.downloading, false);
+    assert.equal(ready.modelPresent, true);
+    assert.equal(ready.error, null);
+});
+
+test('download failures remain visible in status and retry resets the error', async () => {
+    const modelDir = await fs.mkdtemp(path.join(os.tmpdir(), 'nodecast-laya-failure-'));
+    let shouldFail = true;
+    const service = new LayaService({
+        modelDir,
+        cache: null,
+        fetch: async url => {
+            if (url.endsWith('/health')) throw new Error('connection refused at https://secret.invalid/token');
+            if (shouldFail) throw new Error('download failed at https://secret.invalid/token');
+            return { ok: true, json: async () => ({ answers: {} }) };
+        }
+    });
+
+    service.startModelDownload();
+    await service.downloadPromise;
+    const failed = await service.status();
+    assert.equal(failed.phase, 'failed');
+    assert.equal(failed.downloading, false);
+    assert.equal(failed.error.message, 'Laya runtime is unavailable');
+    assert.doesNotMatch(JSON.stringify(failed), /secret\.invalid|token/);
+
+    shouldFail = false;
+    const retry = service.startModelDownload();
+    assert.equal(retry.error, null);
+    assert.equal(retry.lastError, null);
+    await service.downloadPromise;
 });
 
 test('model deletion remains limited to the configured model directory', async () => {
@@ -30,10 +101,16 @@ test('model deletion remains limited to the configured model directory', async (
     await fs.writeFile(path.join(modelDir, 'nested', 'model.bin'), 'model');
     await fs.writeFile(sentinel, 'keep');
 
-    await clearDirectoryContents(modelDir);
+    const service = new LayaService({ modelDir, cache: null, fetch: async () => { throw new Error('offline'); } });
+    service.downloadState.phase = 'failed';
+    service.downloadState.error = { message: 'previous error', detail: 'safe' };
+    const deleted = await service.deleteModel();
 
     assert.deepEqual(await fs.readdir(modelDir), []);
     assert.equal(await fs.readFile(sentinel, 'utf8'), 'keep');
+    assert.equal(deleted.phase, 'idle');
+    assert.equal(deleted.error, null);
+    assert.equal(deleted.sizeBytes, 0);
 });
 
 test('batch validation rejects oversized item counts', () => {