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

org/detection.org

@@ -48,7 +48,7 @@ See =docs/plans/2026-05-11-terminal-detection.md= for implementation tasks.
 * Tests
 
 #+BEGIN_SRC lisp :tangle no
-;; Tests are manually added to backend/tests.lisp
+;; Tests are manually added to src/backend/tests.lisp
 (def-test detection-returns-backend-instance ()
   (let ((be (cl-tty.backend:detect-backend)))
     (is-true (typep be 'cl-tty.backend:backend))))
@@ -70,7 +70,7 @@ No new package definition needed.
 
 Check ~COLORTERM~ first — it's the simplest and most reliable signal.
 
-#+BEGIN_SRC lisp :tangle ../backend/detection.lisp
+#+BEGIN_SRC lisp :tangle ../src/backend/detection.lisp
 (in-package :cl-tty.backend)
 
 ;;; ─── Detection cache ────────────────────────────────────────────────────────
@@ -94,7 +94,7 @@ Returns :modern if COLORTERM contains 'truecolor' or '24bit', nil otherwise."
 
 Check if stdout is connected to a terminal (not a pipe or file).
 
-#+BEGIN_SRC lisp :tangle ../backend/detection.lisp
+#+BEGIN_SRC lisp :tangle ../src/backend/detection.lisp
 ;;; ─── TTY probe ──────────────────────────────────────────────────────────────
 
 (defun detect-backend-by-tty ()
@@ -119,7 +119,7 @@ Fix: Write queries to ~*standard-output*~ and read responses from
 ~*standard-input*~.  This matches where the terminal actually delivers its
 DA1/DA3 response bytes.
 
-#+BEGIN_SRC lisp :tangle ../backend/detection.lisp
+#+BEGIN_SRC lisp :tangle ../src/backend/detection.lisp
 ;;; ─── DA1 terminal query ─────────────────────────────────────────────────────
 
 (defun query-terminal (query &optional (timeout 0.1))
@@ -149,7 +149,7 @@ Returns T if terminal reports kitty compatibility codes."
 
 Tie all probes together into ~detect-backend~.
 
-#+BEGIN_SRC lisp :tangle ../backend/detection.lisp
+#+BEGIN_SRC lisp :tangle ../src/backend/detection.lisp
 ;;; ─── Orchestrator ───────────────────────────────────────────────────────────
 
 (defun detect-backend ()