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

src/components/dialog-package.lisp

@@ -0,0 +1,32 @@
+;;; dialog-package.lisp — Package definition for cl-tty.dialog
+
+(defpackage :cl-tty.dialog
+  (:use :cl :cl-tty.input :cl-tty.select)
+  (:export
+   #:dialog
+   #:dialog-title
+   #:dialog-content
+   #:dialog-on-dismiss
+   #:dialog-size
+   #:dialog-size-pixels
+   #:render-dialog
+   #:push-dialog
+   #:pop-dialog
+   #:*dialog-stack*
+   #:alert-dialog
+   #:confirm-dialog
+   #:select-dialog
+   #:prompt-dialog
+   #:toast
+   #:toast-message
+   #:toast-variant
+   #:render-toast
+   #:dismiss-toast
+   #:*toasts*
+   ;; Tests
+   #:dialog-create
+   #:dialog-size-small
+   #:dialog-size-medium
+   #:dialog-push-pop
+   #:toast-create
+   #:toast-dismiss))