Rename cl-tui -> cl-tty, v0.9.0: Dialog System + Toast

Rename: cl-tty avoids naming collision with Quicklisp's cl-tui (naryl/cl-tui,
a cl-charms-based ncurses library). Our project is pure escape-sequence CL.

v0.9.0 adds:
- Dialog base class: modal overlay with backdrop, centered panel, size
  variants (:small/:medium/:large), stack-based management
- Dialog subclasses: alert, confirm, select-dialog, prompt-dialog
- Toast notifications: transient, top-right corner, auto-dismiss,
  colored variants (info/success/warning/error)
- 78 tests total, 100% passing

ASDF: read-time package references (+fiveam:+) replaced with
find-symbol so .asd loads without FiveAM pre-loaded

tests/markdown-tests.lisp

@@ -1,15 +1,15 @@
-;;; markdown-tests.lisp — Tests for cl-tui.markdown
+;;; markdown-tests.lisp — Tests for cl-tty.markdown
 
-(defpackage :cl-tui-markdown-test
-  (:use :cl :cl-tui.markdown :fiveam))
+(defpackage :cl-tty-markdown-test
+  (:use :cl :cl-tty.markdown :fiveam))
 
-(in-package :cl-tui-markdown-test)
+(in-package :cl-tty-markdown-test)
 
 ;; Test suite
-(def-suite :cl-tui-markdown-test
-  :description "Markdown parser/renderer tests for cl-tui.markdown")
+(def-suite :cl-tty-markdown-test
+  :description "Markdown parser/renderer tests for cl-tty.markdown")
 
-(in-suite :cl-tui-markdown-test)
+(in-suite :cl-tty-markdown-test)
 
 ;; ─── Parser tests ─────────────────────────────────────────────────────────────