Replace external dirname/basename with parameter expansion in hot loops

lidarr_missing_art.sh's album-directory-map loop (both the cache-hit and
live-fallback branches) and arr_profile_enforcer.sh's _is_kids_path()
called dirname/basename once per item -- 127K+ tracks and ~4000
series/movies respectively, each call forking a subprocess. Measured:
0.39s vs 72.2s for 20K calls, ~185x. Verified identical output against
real paths (including unicode/space/paren edge cases) before switching.

Tools/arr_profile_enforcer.sh

@@ -104,8 +104,11 @@ exit(1);
 
 _is_kids_path() {
     local path="$1"
-    local dir
-    dir=$(basename "$(dirname "$path")")
+    # Parameter expansion instead of external dirname+basename — called once per series/movie
+    # (~4000 items combined), each call was forking two subprocesses. Measured 2026-07-17:
+    # ~185x faster per equivalent call (0.39s vs 72.2s per 20K) for the identical result.
+    local parent="${path%/*}"
+    local dir="${parent##*/}"
     [[ "$dir" == *kids* || "$dir" == *anime* ]]
 }