Round-off: README render routes, tune scripts create midi/ if missing

Fresh-clone test passes end-to-end: clone -> build_all.sh -> all four
tunes generate, verify, render and pass audio checks with no prior state.

tunes/01_service_station_2am.py

@@ -137,6 +137,7 @@ def build():
 
 
 if __name__ == "__main__":
+    os.makedirs(os.path.dirname(OUT), exist_ok=True)
     mf = build()
     mf.write(OUT)
     d = verify(OUT, min_sec=40, max_sec=120)

tunes/02_kestrel_over_the_fens.py

@@ -109,6 +109,7 @@ def build():
 
 
 if __name__ == "__main__":
+    os.makedirs(os.path.dirname(OUT), exist_ok=True)
     mf = build()
     mf.write(OUT)
     d = verify(OUT, min_sec=50, max_sec=150)

tunes/03_late_equaliser.py

@@ -133,6 +133,7 @@ def build():
 
 
 if __name__ == "__main__":
+    os.makedirs(os.path.dirname(OUT), exist_ok=True)
     mf = build()
     mf.write(OUT)
     dd = verify(OUT, min_sec=30, max_sec=120)