passepartout: v0.4.2 Structured Output

Submodule: function-calling API, json-alist-to-plist converter,
tool-calls wiring in think(), diagnostics fix, version bump to 0.4.2.
AGENTS.md: validate with emacs check-parens on org source (not SBCL).

AGENTS.md

@@ -20,7 +20,7 @@ Tangle a single file:
   emacs --batch --eval "(progn (require 'org) (find-file \"org/FILE.org\") (org-babel-tangle) (kill-buffer))"
 
 Validate structural integrity:
-  sbcl --noinform --eval '(with-open-file (f "lisp/FILE.lisp") (loop (read f nil (return))))' --quit
+  emacs --batch -Q --eval '(progn (find-file "org/FILE.org") (check-parens) (kill-buffer))'
 
 Run tests:
   sbcl --noinform \
@@ -48,3 +48,4 @@ When REPL is down: fall back to the SBCL cycle above.
 - Prove RED before writing implementation
 - Validate before committing
 - If a tool fails, explain why and ask before trying alternatives
+- Before shipping a version, run the `** File Update Checklist` in `docs/ROADMAP.org`