v0.0.1: backend protocol — abstraction layer + simple backend

Implement the backend protocol with two backends (modern planned,
simple done). Includes package definitions, CLOS generic protocol,
simple-backend with ASCII borders, and 9 FiveAM tests.

RED: 9/9 tests failing (no implementation)
GREEN: 9/9 tests passing

- backend/package.lisp — defpackage, exports
- backend/classes.lisp — backend base class, 18 generics
- backend/simple.lisp — simple-backend implementation
- backend/tests.lisp — 9 FiveAM test cases
- org/backend-protocol.org — literate source

docs/ROADMAP.org

@@ -5,10 +5,81 @@
 * The Roadmap
 
 Each phase is one minor release. Phases ship in dependency order — each depends on
-the components from prior phases. The layout engine ships first because everything
-else builds on it.
+the components from prior phases. The backend protocol ships first because
+everything else builds on it.
 
-Feature releases increment the minor version (v0.X.0). Bugfix releases increment
+** v0.0.1: Foundation — Backend Protocol
+
+The abstraction layer that makes everything portable. Two backends:
+=modern= (raw escape sequences, truecolor, modern features) and =simple=
+(ASCII art, universal compatibility). The component tree never touches
+the terminal directly — it dispatches through the protocol.
+
+*** TODO Backend protocol definition
+:PROPERTIES:
+:ID:       id-v000-protocol
+:CREATED:  [2026-05-10 Sat]
+:END:
+
+- Define =backend= abstract class with generic functions:
+  - =initialize-backend=, =shutdown-backend=, =suspend-backend=, =resume-backend=
+  - =backend-size=, =backend-write=, =backend-clear=
+  - =begin-sync=, =end-sync= — DECICM synchronized updates
+  - =draw-rect=, =draw-text=, =draw-border=, =draw-ellipsis=, =draw-link=
+  - =cursor-move=, =cursor-hide=, =cursor-show=, =cursor-style=
+  - =read-event=, =enable-mouse=, =enable-bracketed-paste=, =set-keyboard-mode=
+  - =capable-p= — query feature support
+- Style plist structure: ~(:fg :error :bg :background-panel :bold t :italic nil ...)~
+- ~100 lines
+
+*** TODO Simple backend
+:PROPERTIES:
+:ID:       id-v000-simple
+:CREATED:  [2026-05-10 Sat]
+:END:
+
+- =simple-backend= class — inherits =backend=
+- Borders: ASCII (~+-|~), no rounded corners
+- No color, no bold/italic — plain characters only
+- No OSC 8 links, no mouse, no synchronized updates
+- Works on any terminal, any SSH connection, piped output
+- ~100 lines
+
+*** TODO Modern backend
+:PROPERTIES:
+:ID:       id-v000-modern
+:CREATED:  [2026-05-10 Sat]
+:END:
+
+- =modern-backend= class — inherits =backend=
+- Truecolor 24-bit foreground/background
+- Rounded, single, double border styles via Unicode box-drawing
+- OSC 8 hyperlinks (clickable URLs)
+- DECICM synchronized updates (flicker-free)
+- SGR mouse tracking + kitty keyboard protocol
+- Bracketed paste detection
+- Bold, italic, underline, dim, blink, reverse, strikethrough
+- Cursor style: =:bar=, =:block=, =:underline=, with blink option
+- ~250 lines
+
+*** TODO Terminal capability detection
+:PROPERTIES:
+:ID:       id-v000-detection
+:CREATED:  [2026-05-10 Sat]
+:END:
+
+- =detect-backend= → returns =modern-backend= or =simple-backend=
+- Check if stdout is a TTY (if not → =simple-backend=)
+- Send DA1 (~ESC[c~) query, 100ms timeout
+- Send DA3 (~ESC[?c~) for kitty/wezterm identification
+- Query DECRPM (~ESC[?2026$p~) for DECICM sync support
+- Query truecolor support via =COLORTERM= env var + DA response
+- Cache detection result so subsequent calls are instant
+- ~100 lines
+
+~550 lines total. Dependencies: None (pure CL, no FFI, no external libs).
+
+** v0.0.2: Layout Engine
 the patch version (v0.X.Y).
 
 ** File Update Checklist