Add org-skill-self-edit: self-repair with paren balancing

- New skill hooks into :syntax-error and :repair-request events
- Deterministic paren balancing (fast fix)
- Surgical file edits with memory rollback on failure
- :self-edit and :balance-parens cognitive tools
- 9 new tests, all 93 tests passing

library/package.lisp

@@ -122,6 +122,10 @@
     #:emacs-edit-id-format
     #:emacs-edit-set-property
     #:emacs-edit-set-todo
+
+    ;; --- Self-Edit Skill ---
+    #:self-edit-balance-parens
+    #:self-edit-apply
     
     ;; --- Security Vault ---
    #:vault-get-secret