v0.12.0: Terminal capability detection, GPL 3.0 license, roadmap rewrite

LICENSE:
- Added GNU General Public License v3.0
- Updated README.org to reflect GPL 3.0

ROADMAP:
- Complete rewrite to reflect actual project state
- Removed croatoan/ncurses/Yoga FFI references
- Marked all 11 existing versions DONE
- Added v0.12.0-0.14.0 for new features (detection, pipeline, mouse)

DETECTION (v0.12.0):
- detect-backend: auto-detect modern vs simple backend
- detect-backend-by-env: check COLORTERM env var
- detect-backend-by-tty: check interactive-stream-p
- detect-backend-by-da1: query terminal via ESC[c (best-effort)
- *detected-backend* cache for zero-cost subsequent calls
- Added detection.lisp to ASDF and package exports
- Added 2 new tests (360 total, all passing)
- demo.lisp updated to use detect-backend

ORG BACKPORT (pre-existing fixes synced):
- dialog.org: render-dialog/render-toast fixes, class initforms
- scrollbox-tabbar.org: background-element -> bright-black, remove duplicate render
- select.org: remove duplicate render export
- text-input.org: remove duplicate %split-string, undo overflow fix
- layout-engine.org: quoted-literal -> list constructors, normalize-box rewrite
- mouse.org: add missing exports, fix test

backend/detection.lisp

@@ -0,0 +1,62 @@
+(in-package :cl-tty.backend)
+
+;;; ─── Detection cache ────────────────────────────────────────────────────────
+
+(defvar *detected-backend* nil
+  "Cached backend instance from detect-backend. Nil = not yet detected.")
+
+;;; ─── Environment probe ──────────────────────────────────────────────────────
+
+(defun detect-backend-by-env ()
+  "Check COLORTERM environment variable for modern terminal support.
+Returns :modern if COLORTERM contains 'truecolor' or '24bit', nil otherwise."
+  (let ((colorterm (sb-ext:posix-getenv "COLORTERM")))
+    (when (and colorterm
+               (or (search "truecolor" colorterm :test #'char-equal)
+                   (search "24bit" colorterm :test #'char-equal)))
+      :modern)))
+
+;;; ─── TTY probe ──────────────────────────────────────────────────────────────
+
+(defun detect-backend-by-tty ()
+  "Check if stdout is a real terminal (not a pipe/redirect).
+Returns T if stdout is interactive, nil otherwise."
+  (interactive-stream-p *standard-output*))
+
+;;; ─── DA1 terminal query ─────────────────────────────────────────────────────
+
+(defun query-terminal (query &optional (timeout 0.1))
+  "Send QUERY string to terminal and return any response received within
+TIMEOUT seconds. Returns the response string, or nil if no response."
+  (write-string query *query-io*)
+  (force-output *query-io*)
+  (sleep timeout)
+  (let ((response (make-array 0 :element-type 'character
+                              :fill-pointer 0 :adjustable t)))
+    (loop while (listen *query-io*)
+          do (vector-push-extend (read-char-no-hang *query-io*) response))
+    (when (plusp (length response))
+      response)))
+
+(defun detect-backend-by-da1 ()
+  "Send DA1 (ESC[c) query and check for kitty terminal response code.
+Returns T if terminal reports kitty compatibility codes."
+  (let ((response (query-terminal (format nil "~C[c" #\Esc))))
+    (when response
+      ;; DA1 response format: ESC [ ? digits ; digits c
+      ;; Kitty reports code 62 in the response
+      (search "?62" response))))
+
+;;; ─── Orchestrator ───────────────────────────────────────────────────────────
+
+(defun detect-backend ()
+  "Auto-detect the appropriate backend for the current terminal.
+Returns a backend instance (modern-backend or simple-backend).
+Result is cached in *detected-backend* for subsequent calls."
+  (or *detected-backend*
+      (setf *detected-backend*
+            (if (and (detect-backend-by-tty)
+                     (or (eql (detect-backend-by-env) :modern)
+                         (detect-backend-by-da1)))
+                (make-modern-backend)
+                (make-simple-backend)))))

backend/package.lisp

@@ -21,6 +21,8 @@
    #:make-simple-backend
    ;; Modern backend
    #:modern-backend #:make-modern-backend
+   ;; Detection
+   #:detect-backend #:*detected-backend*
    ;; Internal (for testing)
    #:sgr-fg #:sgr-bg #:sgr-attr
    #:cursor-move-escape #:cursor-style-escape

backend/tests.lisp

@@ -136,3 +136,16 @@
     (shutdown-backend b)
     (is (string= (get-output-stream-string s) "")
         "draw-rect is a no-op on simple-backend")))
+
+;; ── Detection ──────────────────────────────────────────────────
+
+(test detection-returns-backend-instance
+  "detect-backend returns a valid backend instance"
+  (let ((be (cl-tty.backend:detect-backend)))
+    (is (typep be 'cl-tty.backend:backend))))
+
+(test detection-caches-result
+  "detect-backend caches the result in *detected-backend*"
+  (let ((*detected-backend* nil))
+    (cl-tty.backend:detect-backend)
+    (is-true (not (null cl-tty.backend::*detected-backend*)))))