refactor(web): drop a length check the closed-set parse already makes (#61)

The read is capped at 17 bytes and no valid language is longer than 4, so the parse
refuses anything the length check would; the mutant that removed it survived.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/web/uploads.go

@@ -36,7 +36,7 @@ const (
 	// and the title field; the cap itself is enforced on the file part by Intake.
 	uploadOverhead = 1 << 20
 	maxTitleRunes  = 200
-	// maxLanguageBytes bounds the language field: the longest value is four bytes.
+	// maxLanguageBytes bounds what is read of the language field; a valid value is at most four bytes, so a longer one fails the parse.
 	maxLanguageBytes = 16
 	// uploadPollEvery is how often an unfinished upload re-asks for its status.
 	uploadPollEvery = "2s"
@@ -136,7 +136,7 @@ func (a *App) handleUploadPost(w http.ResponseWriter, r *http.Request) {
 				return
 			}
 			l, ok := domain.ParseLanguage(string(b))
-			if !ok || len(b) > maxLanguageBytes {
+			if !ok {
 				a.logger().Info("upload rejected", "reason", "language")
 				a.renderUploadsPage(w, r, userID, http.StatusBadRequest, "Choose a language from the list.")
 				return