check-parens: standalone paren balance checker for lisp blocks in org files

Scans #+begin_src lisp ... #+end_src blocks, strips strings and
comments, reports unbalanced parens per-block with line numbers.
Detects unterminated blocks (no matching #+end_src).

Zero dependencies (stdlib Python). Called from AGENTS.md step:
  projects/check-parens/check-parens org/file.org

projects/check-parens/README.org

@@ -0,0 +1,42 @@
+#+TITLE: check-parens
+#+FILETAGS: :tool:lisp:org:
+
+Standalone parentheseis checker for Lisp source blocks in Org files.
+
+Scans all ~#+begin_src lisp … #+end_src~ blocks in an Org file, strips
+string and comment content, and reports unbalanced parentheses per block.
+
+== Usage
+
+#+begin_src shell
+  check-parens <file.org> [<file.org> ...]
+  check-parens -v <file.org>
+#+end_src
+
+Exit 0 if all blocks are balanced and terminated, 1 otherwise.
+
+== Output
+
+  ~file.org: OK~ — all blocks balanced
+  ~file.org: Block at line 27: +2 (missing 2 closes) — near …~
+  ~file.org: Block at line 103: unterminated — no matching #+end_src~
+
+The ~-v~ flag prints the full block content for each issue.
+
+== Integration
+
+Pre-commit hook:
+
+#+begin_src shell
+  cat > .git/hooks/pre-commit <<'HOOK'
+  #!/bin/sh
+  for f in $(git diff --cached --name-only --diff-filter=ACM | grep '\.org$'); do
+    projects/check-parens/check-parens "$f" || exit 1
+  done
+  HOOK
+  chmod +x .git/hooks/pre-commit
+#+end_src
+
+== Dependencies
+
+None (stdlib Python 3).