fix: ensure profile directory exists before writing

Creates profile directory in profile and explain targets to prevent
errors on first run.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Makefile

@@ -22,9 +22,11 @@ run: it
 	@ ./lambda - < ./samples/$(TEST).txt > program.out
 
 profile: it
+	@ mkdir -p profile
 	@ ./lambda -p profile/cpu.prof - < ./samples/$(TEST).txt > program.out
 
 explain: it
+	@ mkdir -p profile
 	@ ./lambda -x -p profile/cpu.prof - < ./samples/$(TEST).txt > program.out
 
 graph: