feat(captions): P1/P2 improvements - region variant fallback, DownloadInfo init, subtitle_files UI

P1 fixes:
- _subtitle_lang_list now extracts base language from qualified tags
  (e.g. zh-Hans → zh base) so regional variants are still added as
  fallbacks. Original input is preserved as first priority.
- DownloadInfo.__init__ now explicitly initializes filename=None and
  chapter_files=[] to avoid AttributeError on dynamic attribute access.
- __setstate__ adds filename=None migration for old persistent data.
- Frontend Download interface gains subtitle_files field; completed
  downloads show each subtitle file with download link and CC icon.

P2 improvements:
- _LANGUAGE_REGION_VARIANTS expanded from 10 to 30 languages covering
  it/ja/ko/hi/th/vi/id/pl/uk/ru/cs/sv/da/no/fi/tr/el/he/hu/bn/ta.
- Languages with no regional variants use empty tuple (they still get
  -orig suffix when include_orig=True).

app/dl_formats.py

@@ -25,6 +25,27 @@ _LANGUAGE_REGION_VARIANTS = {
     "nl": ("NL", "BE"),
     "ro": ("RO", "MD"),
     "ms": ("MY", "BN", "SG"),
+    "it": ("IT", "SM"),
+    "ja": (),
+    "ko": (),
+    "hi": (),
+    "th": (),
+    "vi": (),
+    "id": (),
+    "pl": (),
+    "uk": (),
+    "ru": ("RU", "BY", "KZ", "UA"),
+    "cs": (),
+    "sv": ("SE", "FI"),
+    "da": ("DK",),
+    "no": ("NO", "NB", "NN"),
+    "fi": (),
+    "tr": (),
+    "el": ("GR", "CY"),
+    "he": (),
+    "hu": (),
+    "bn": ("BD", "IN"),
+    "ta": ("IN", "SG", "LK", "MY"),
 }
 
 
@@ -34,13 +55,27 @@ def _subtitle_lang_list(language: str, include_orig: bool = False) -> list[str]:
     Starts with the exact language, then appends common regional variants
     (e.g. ``en`` → ``en-US, en-GB, en-AU, …``).  ``include_orig`` adds the
     ``<lang>-orig`` tag that YouTube uses for original-language auto-captions.
+
+    Handles user input that already contains a region or script subtag (e.g.
+    ``zh-Hans``, ``pt-BR``): extracts the base language (``zh``, ``pt``) so
+    regional variants for that base language are still included as fallbacks.
     """
     langs = [language]
-    variants = _LANGUAGE_REGION_VARIANTS.get(language)
+    # Extract base language (e.g. "zh-Hans" → "zh", "en-GB" → "en")
+    base = language.split('-')[0]
+    # If user provided a qualified tag, also include the base form as fallback
+    if base != language:
+        langs.append(base)
+    variants = _LANGUAGE_REGION_VARIANTS.get(base)
     if variants:
-        langs.extend(f"{language}-{region}" for region in variants)
+        for region in variants:
+            variant = f"{base}-{region}"
+            if variant not in langs:
+                langs.append(variant)
     if include_orig:
-        langs.append(f"{language}-orig")
+        orig_tag = f"{base}-orig"
+        if orig_tag not in langs:
+            langs.append(orig_tag)
     return langs
 
 

app/tests/test_dl_formats.py

@@ -114,7 +114,7 @@ class DlFormatsTests(unittest.TestCase):
         opts = get_opts(
             "captions", "auto", "srt", "best", {}, subtitle_language="it", subtitle_mode="prefer_manual"
         )
-        self.assertEqual(opts["subtitleslangs"], ["it", "it-orig"])
+        self.assertEqual(opts["subtitleslangs"], ["it", "it-IT", "it-SM", "it-orig"])
 
     def test_get_opts_captions_txt_maps_to_srt_format(self):
         opts = get_opts("captions", "auto", "txt", "best", {})

app/ytdl.py

@@ -210,6 +210,7 @@ class DownloadInfo:
         self.size = None
         self.timestamp = time.time_ns()
         self.error = error
+        self.filename = None
         # Strip non-pickleable values (generators, iterators, locks, etc.) for shelve
         self.entry = _sanitize_entry_for_pickle(entry) if entry is not None else None
         self.playlist_item_limit = playlist_item_limit
@@ -221,6 +222,7 @@ class DownloadInfo:
         self.ytdl_options_overrides = dict(ytdl_options_overrides or {})
         self.clip_start = clip_start
         self.clip_end = clip_end
+        self.chapter_files = []
         self.subtitle_files = []
 
     def __setstate__(self, state):
@@ -289,6 +291,8 @@ class DownloadInfo:
             self.subtitle_files = []
         if not hasattr(self, "chapter_files"):
             self.chapter_files = []
+        if not hasattr(self, "filename"):
+            self.filename = None
         if not hasattr(self, "clip_start"):
             self.clip_start = None
         if not hasattr(self, "clip_end"):

ui/src/app/app.html

@@ -904,7 +904,36 @@
           </td>
         </tr>
         }
-      }
+        }
+        @if (entry[1].subtitle_files && entry[1].subtitle_files.length > 0) {
+          @for (subtitleFile of entry[1].subtitle_files; track subtitleFile.filename) {
+            <tr [class.disabled]='entry[1].deleting'>
+              <td></td>
+              <td>
+                <div style="padding-left: 2rem;">
+              <fa-icon [icon]="faClosedCaptioning" class="text-info me-2" />
+              <a href="{{buildChapterDownloadLink(entry[1], subtitleFile.filename)}}" target="_blank" [attr.aria-label]="'Open subtitle file ' + getChapterFileName(subtitleFile.filename)">{{
+                getChapterFileName(subtitleFile.filename) }}</a>
+            </div>
+          </td>
+          <td></td>
+          <td></td>
+          <td></td>
+          <td>
+            @if (subtitleFile.size) {
+            <span>{{ subtitleFile.size | fileSize }}</span>
+            }
+          </td>
+          <td></td>
+          <td>
+            <div class="d-flex">
+              <a href="{{buildChapterDownloadLink(entry[1], subtitleFile.filename)}}" download [attr.aria-label]="'Download subtitle file ' + getChapterFileName(subtitleFile.filename)"
+                class="btn btn-link"><fa-icon [icon]="faDownload" /></a>
+            </div>
+          </td>
+        </tr>
+        }
+        }
     }
       </tbody>
     </table>

ui/src/app/app.ts

@@ -7,7 +7,7 @@ import { takeUntilDestroyed } from '@angular/core/rxjs-interop';
 import { FontAwesomeModule } from '@fortawesome/angular-fontawesome';
 import { NgbModule } from '@ng-bootstrap/ng-bootstrap';
 import { NgSelectModule } from '@ng-select/ng-select';  
-import { faTrashAlt, faCheckCircle, faTimesCircle, faRedoAlt, faSun, faMoon, faCheck, faCircleHalfStroke, faDownload, faExternalLinkAlt, faFileImport, faFileExport, faCopy, faClock, faTachometerAlt, faSortAmountDown, faSortAmountUp, faChevronRight, faChevronDown, faUpload, faPause, faPlay } from '@fortawesome/free-solid-svg-icons';
+import { faTrashAlt, faCheckCircle, faTimesCircle, faRedoAlt, faSun, faMoon, faCheck, faCircleHalfStroke, faDownload, faExternalLinkAlt, faFileImport, faFileExport, faCopy, faClock, faTachometerAlt, faSortAmountDown, faSortAmountUp, faChevronRight, faChevronDown, faUpload, faPause, faPlay, faClosedCaptioning } from '@fortawesome/free-solid-svg-icons';
 import { faGithub } from '@fortawesome/free-brands-svg-icons';
 import { CookieService } from 'ngx-cookie-service';
 import { AddDownloadPayload, DownloadsService } from './services/downloads.service';
@@ -188,6 +188,7 @@ export class App implements AfterViewInit, OnInit, OnDestroy {
   faUpload = faUpload;
   faPause = faPause;
   faPlay = faPlay;
+  faClosedCaptioning = faClosedCaptioning;
   subtitleLanguages = [
     { id: 'en', text: 'English' },
     { id: 'ar', text: 'Arabic' },

ui/src/app/interfaces/download.ts

@@ -31,4 +31,5 @@ export interface Download {
   error?: string;
   deleting?: boolean;
   chapter_files?: { filename: string, size: number }[];
+  subtitle_files?: { filename: string, size: number }[];
 }