refactor(release): freeze ParsedRelease + enrich_from_probe returns new instance

ParsedRelease is now @dataclass(frozen=True). The enrichment passes that
used to patch fields in place now produce new instances:

- enrich_from_probe(parsed, info, kb) returns a new ParsedRelease via
  dataclasses.replace (no allocation when no field changed).
- inspect_release rebinds 'parsed' after detect_media_type (wrapped in
  MediaTypeToken — the strict isinstance check now also runs on
  replace) and after enrich_from_probe.

languages becomes a tuple[str, ...] so the VO is properly immutable.
Parser pipeline packs languages as a tuple in the assemble dict.

Callers updated: inspect_release, testing/recognize_folders_in_downloads.py.
Tests updated: 22 enrich_from_probe call sites rebound, language
assertions switched to tuple literals, test_release_fixtures normalizes
result['languages'] back to list for YAML-fixture comparison.

Suite: 1077 passed.

testing/recognize_folders_in_downloads.py

@@ -100,9 +100,12 @@ def main() -> None:
         print(c(f"Error: {downloads} does not exist", RED), file=sys.stderr)
         sys.exit(1)
 
+    from dataclasses import replace
+
     from alfred.application.release.detect_media_type import detect_media_type
     from alfred.application.release.enrich_from_probe import enrich_from_probe
     from alfred.domain.release.services import parse_release
+    from alfred.domain.release.value_objects import MediaTypeToken
     from alfred.infrastructure.filesystem.find_video import find_video_file
     from alfred.infrastructure.knowledge.release_kb import YamlReleaseKnowledge
     from alfred.infrastructure.probe import FfprobeMediaProber
@@ -126,13 +129,13 @@ def main() -> None:
 
         try:
             p, _report = parse_release(name, _kb)
-            p.media_type = detect_media_type(p, entry, _kb)
+            p = replace(p, media_type=MediaTypeToken(detect_media_type(p, entry, _kb)))
             if p.media_type not in ("unknown", "other"):
                 video_file = find_video_file(entry)
                 if video_file:
                     media_info = _prober.probe(video_file)
                     if media_info:
-                        enrich_from_probe(p, media_info, _kb)
+                        p = enrich_from_probe(p, media_info, _kb)
             warnings = _assess(p)
         except Exception as e:
             warnings = [f"parse error: {e}"]