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 ''.

CHANGELOG.md

@@ -15,6 +15,14 @@ callers).
 
 ## [Unreleased]
 
+### Fixed
+
+- **`enrich_from_probe` now refreshes `tech_string`** after filling
+  `quality` / `source` / `codec`. Previously the field stayed at its
+  parser-time value, so filename builders saw stale tech tokens even
+  after a successful probe. New `TestTechString` class in
+  `tests/application/test_enrich_from_probe.py` locks the behavior.
+
 ### Added
 
 - **`inspect_release` orchestrator + `InspectedResult` VO**