feat(tools): add a reproducible terminal capture harness

Records on a throwaway Xvfb display at fixed geometry, drives the session with
xdotool, and quantises through a per-clip palette so the terminal's colours
survive instead of dithering.

tools/record-lib.sh

@@ -0,0 +1,64 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+ROOT=$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)
+FONT=${FONT:-JetBrainsMono Nerd Font Mono}
+FPS=${FPS:-12}
+
+start_xvfb() {
+    local geometry=$1
+    for n in $(seq 90 120); do
+        [ -e "/tmp/.X11-unix/X$n" ] && continue
+        DISPLAY=":$n"
+        Xvfb "$DISPLAY" -screen 0 "${geometry}x24" -nolisten tcp >/dev/null 2>&1 &
+        XVFB_PID=$!
+        export DISPLAY XVFB_PID
+        for _ in $(seq 50); do
+            xdotool getdisplaygeometry >/dev/null 2>&1 && return 0
+            sleep 0.1
+        done
+        kill "$XVFB_PID" 2>/dev/null || true
+    done
+    echo "no free X display" >&2
+    exit 1
+}
+
+start_capture() {
+    local geometry=$1 out=$2
+    ffmpeg -v error -y -f x11grab -draw_mouse 0 -framerate "$FPS" \
+        -video_size "$geometry" -i "$DISPLAY" -codec:v libx264 -preset ultrafast \
+        -qp 0 "$out" >/dev/null 2>&1 &
+    FFMPEG_PID=$!
+    export FFMPEG_PID
+    sleep 1
+}
+
+stop_capture() {
+    kill -INT "$FFMPEG_PID" 2>/dev/null || true
+    wait "$FFMPEG_PID" 2>/dev/null || true
+}
+
+send_line() {
+    local text=$1 pause=${2:-0.9}
+    xdotool type --delay 42 -- "$text"
+    sleep 0.35
+    xdotool key Return
+    sleep "$pause"
+}
+
+to_gif() {
+    local src=$1 out=$2 fps=${3:-11}
+    local palette=${src%.mkv}.png
+    ffmpeg -v error -y -i "$src" -vf "fps=$fps,palettegen=stats_mode=diff" "$palette"
+    ffmpeg -v error -y -i "$src" -i "$palette" \
+        -lavfi "fps=$fps[x];[x][1:v]paletteuse=dither=none:diff_mode=rectangle" \
+        -loop 0 "$out"
+    rm -f "$palette"
+}
+
+cleanup() {
+    kill "${FFMPEG_PID:-}" 2>/dev/null || true
+    kill "${XVFB_PID:-}" 2>/dev/null || true
+}
+trap cleanup EXIT