fix(media): a shelf needs a name, so a mistagged chapter number parks

Plex's artist row for 272 chapters is a chapter number the ripper put in the
artist tag (0.4, 31, 05), which would have filed them under a shelf called 0.4.
A narrator is a person, so it must contain a letter; the same test is deliberately
not applied to a book title, which may honestly be 1984.

tests/media_audiobooks.bats

@@ -142,6 +142,10 @@ setup() {
     row "$H/Rip/tape.mp3" "Ann Reader" "Unknown album (03/03/2015 21:39:55)" "" 1 "One"
     row "$H/NoWho/Real Book.mp3" "[Unknown Artist]" "A Named Book" 2001 1 "One"
     row "$H/Multicast/Genesis.mp3" "Various Artists" "The Bible" "" 1 "Genesis"
+    at "$H/Numbered/01 - Grimoire.mp3" 9000
+    at "$H/Digits/1984.mp3" 9000
+    row "$H/Numbered/01 - Grimoire.mp3" "0.4" "Grimoire of the Lamb" "" 1 "One"
+    row "$H/Digits/1984.mp3" "Ann Reader" "1984" 1949 1 "One"
 
     # The enum TSV is what scripts/media-census.py enumerate writes: bytes, ext,
     # path, no header.
@@ -358,6 +362,16 @@ PY
         "$AB/Various Artists/The Bible/Genesis.mp3" ]
 }
 
+@test "a chapter number mistagged as the narrator parks" {
+    plan
+    [ "$(kind "$H/Numbered/01 - Grimoire.mp3")" = "park" ]
+}
+
+@test "a book whose title is digits still files, because only a name must have a letter" {
+    plan
+    [ "$(dst "$H/Digits/1984.mp3")" = "$AB/Ann Reader/1984 (1949)/1984.mp3" ]
+}
+
 @test "the row, not the extension, decides what a chapter is" {
     plan
     [ "$(kind "$G/NoExt/part01")" = "chapter" ]