fix(.gitignore): unblock bin/*.ml and bin/dune from gitignore

/bin/ was silently making `git add bin/main.ml` require -f even though
bin/main.ml is tracked source. Add negation patterns so OCaml sources
and the dune file inside bin/ are always addable without -f.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: hyperpolymath

.gitignore

@@ -52,6 +52,8 @@ __pycache__/
 *.ali
 /obj/
 /bin/
+!bin/*.ml
+!bin/dune
 
 # Haskell
 /.stack-work/