feat(library-slow-mode): Library providers can now declare "slow mode" for high latency operations

tests/js/v3_slow_provider_loading.test.js

@@ -0,0 +1,36 @@
+// Pins the slow-library-provider loading states in the classic and v3 library
+// surfaces. Providers can declare `slow: true`; the UI should show explicit
+// wait copy plus a status region instead of silently blanking while fetches run.
+
+'use strict';
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const root = path.join(__dirname, '..', '..');
+const SONGS = fs.readFileSync(path.join(root, 'static', 'v3', 'songs.js'), 'utf8');
+const APP = fs.readFileSync(path.join(root, 'static', 'app.js'), 'utf8');
+
+test('v3 Songs slow providers get explicit loading copy', () => {
+    assert.match(SONGS, /function providerLoadingText\(\)[\s\S]*?provider\.slow\s*===\s*true[\s\S]*?this source may take a while\./,
+        'v3 providerLoadingText must branch on provider.slow and explain the longer wait');
+    assert.match(SONGS, /function loadingPanelHtml\(\)[\s\S]*?providerLoadingText\(\)/,
+        'v3 grid loading panel must render the provider-aware loading message');
+});
+
+test('v3 loading indicators are announced as polite status regions', () => {
+    assert.match(SONGS, /function loadingPanelHtml\(\)[\s\S]*?role="status"\s+aria-live="polite"/,
+        'v3 grid loading panel must be a polite status region');
+    assert.match(SONGS, /loadAlbums[\s\S]*role="status"\s+aria-live="polite"[\s\S]*providerLoadingText\(\)/,
+        'v3 albums loading state must be a polite status region');
+    assert.match(SONGS, /loadTree[\s\S]*role="status"\s+aria-live="polite"[\s\S]*providerLoadingText\(\)/,
+        'v3 list loading state must be a polite status region');
+});
+
+test('classic library loading indicator is announced and uses slow provider copy', () => {
+    assert.match(APP, /function _setLibraryLoadingMessage[\s\S]*?role="status"\s+aria-live="polite"/,
+        'classic library loading card must be a polite status region');
+    assert.match(APP, /function _libraryLoadingText\(\)[\s\S]*?provider\.slow\s*===\s*true[\s\S]*?this source may take a while\./,
+        'classic library loading text must branch on provider.slow');
+});

tests/test_library_providers.py

@@ -50,6 +50,7 @@ class FakeLibraryProvider:
     id = "remote:frodo"
     label = "Frodo's Library"
     kind = "remote"
+    slow = True
     capabilities = ("library.read", "art.read", "song.sync")
 
     def __init__(self):
@@ -170,6 +171,7 @@ def test_registered_provider_handles_library_endpoints(server_mod, client):
     assert remote["label"] == "Frodo's Library"
     assert remote["kind"] == "remote"
     assert remote["default"] is False
+    assert remote["slow"] is True
     assert remote["capabilities"] == ["art.read", "library.read", "song.sync"]
 
     songs = client.get("/api/library", params={