fix(release): refresh tech_string after enrich_from_probe

enrich_from_probe fills None fields on ParsedRelease (quality, source,
codec, audio_*, languages) but left tech_string at its parser-time
value — so the filename builders (movie_folder_name, episode_filename,
…) saw stale tech tokens even after a successful probe.

Re-derive tech_string the same way the parser does — quality.source.codec
joined by dots, skipping None — at the end of enrich_from_probe. Token-
level values still win because enrich only fills None fields.

Four new tests in TestTechString cover: enrichment rebuilds it,
existing source survives, no-info input leaves it untouched, fully
empty parsed produces ''.

alfred/application/filesystem/enrich_from_probe.py

@@ -80,3 +80,10 @@ def enrich_from_probe(parsed: ParsedRelease, info: MediaInfo) -> None:
         for lang in info.audio_languages:
             if lang.lower() != "und" and lang.upper() not in existing:
                 parsed.languages.append(lang)
+
+    # Re-derive tech_string so filename builders see the enriched
+    # quality/source/codec. Built the same way as in the parser pipeline:
+    # the non-None parts joined by dots, in order.
+    parsed.tech_string = ".".join(
+        p for p in (parsed.quality, parsed.source, parsed.codec) if p
+    )