fix: TUI undefined-function T crash + add backtrace diagnostics

- Added (push PASSEPARTOUT_DATA_DIR asdf:*central-registry*) before quickload
  so TUI loads from deployed code, not stale Quicklisp cache
- Added :force t to ql:quickload :passepartout/tui to ensure recompilation
- Added handler-bind for undefined-function around tui-main call:
  prints function name + full backtrace, then exits cleanly
- Added sb-debug:print-backtrace to *debugger-hook* for all unhandled errors
- TUI now starts without crash in tmux with TERM=screen-256color

org/core-defpackage.org

@@ -305,6 +305,8 @@ Friendly error handler that replaces the raw SBCL debugger with a diagnostic mes
   (format t "└─────────────────────────────────────────────┘~%")
   (format t "~%")
   (format t "Details: ~A~%" condition)
+  (format t "Backtrace:~%")
+  (sb-debug:print-backtrace :count 20 :stream *standard-output*)
   (finish-output)
   (uiop:quit 1)))
 #+end_src