restructure: move backend/ and layout/ into src/; convert README to org syntax; fix demo package conflict and alien-sap ioctl; update ROADMAP with v0.15.0; remove stale files

- Move backend/ and layout/ directories into src/
- Update all path references in ASD, scripts, docs
- Convert README.org from Markdown syntax to proper Org-mode
- Fix demo.lisp use-package conflict (both backend and input export #:read-event)
- Fix modern-backend TIOCGWINSZ ioctl alien type (alien-sap wrapper)
- Add v0.15.0 section to ROADMAP, update line count to 5760
- Add known gaps (suspend/resume-backend, slot modes) to v1.0.0 checklist
- Remove docs/plans/, debug-layout.lisp, system-index.txt, ci-watchdog.sh
- Move tangle.py to Hermes skill (org-babel-tangle)
- Add .gitignore for fasl files

src/backend/classes.lisp

@@ -0,0 +1,64 @@
+(in-package :cl-tty.backend)
+
+(defclass backend () ())
+
+(defgeneric initialize-backend (backend)
+  (:method ((b backend)) b))
+
+(defgeneric shutdown-backend (backend)
+  (:method ((b backend)) (values)))
+
+(defgeneric backend-size (backend)
+  (:method ((b backend))
+    (values 80 24)))
+
+(defgeneric backend-write (backend string))
+
+(defgeneric backend-clear (backend)
+  (:method ((b backend))
+    (backend-write b (format nil "~C[2J~C[H" #\Esc #\Esc))))
+
+(defgeneric draw-text (backend x y string fg bg &key
+                       bold italic underline reverse dim blink
+                       &allow-other-keys))
+
+(defgeneric draw-border (backend x y width height
+                         &key style fg bg title title-align))
+
+(defgeneric draw-rect (backend x y width height &key bg))
+
+(defgeneric draw-link (backend x y string url &key fg bg))
+
+(defgeneric draw-ellipsis (backend x y width &key fg bg))
+
+(defgeneric cursor-move (backend x y)
+  (:method ((b backend) x y) (declare (ignore x y)) (values)))
+
+(defgeneric cursor-hide (backend)
+  (:method ((b backend)) (values)))
+
+(defgeneric cursor-show (backend)
+  (:method ((b backend)) (values)))
+
+(defgeneric cursor-style (backend shape &key blink)
+  (:method ((b backend) shape &key blink) (values)))
+
+(defgeneric begin-sync (backend)
+  (:method ((b backend)) (values)))
+
+(defgeneric end-sync (backend)
+  (:method ((b backend)) (values)))
+
+(defgeneric read-event (backend &key timeout)
+  (:method ((b backend) &key timeout) (values nil nil)))
+
+(defgeneric enable-mouse (backend)
+  (:method ((b backend)) (values)))
+
+(defgeneric enable-bracketed-paste (backend)
+  (:method ((b backend)) (values)))
+
+(defgeneric capable-p (backend feature)
+  (:method ((b backend) feature)
+    (declare (ignore feature))
+    nil))