Initial commit: Chatter — assistive-writing app for reMarkable Paper Pro Move

Direct-framebuffer ink pipeline (stock-quality strokes), finger-wipe erase,
growable scrolling canvas with color-ghost cleanup, bidirectional toggle with a
persistent 4-finger return launcher, instant button feedback. Includes prebuilt
aarch64 binaries (dist/), build/deploy/install scripts, a user guide, and a
complete technical reference.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/build.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+# Cross-build Chatter with the reMarkable Paper Pro Move (Chiappa) SDK.
+#
+# Usage: scripts/build.sh [extra cmake args]
+# Override SDK location with CHATTER_SDK=...
+set -euo pipefail
+
+SDK="${CHATTER_SDK:-/home/ack/external/remarkable-sdk/chiappa-3.27.0.97}"
+ENV="$SDK/environment-setup-cortexa55-remarkable-linux"
+[ -f "$ENV" ] || { echo "SDK env-setup not found: $ENV"; exit 1; }
+
+cd "$(dirname "$0")/.."
+
+# Yocto SDKs refuse to operate with LD_LIBRARY_PATH set (Jatke sets it globally).
+unset LD_LIBRARY_PATH
+# shellcheck disable=SC1090
+. "$ENV"
+
+cmake -S . -B build "$@"
+cmake --build build -j"$(nproc)"
+echo "built: build/chatter"
+
+# The return-to-Chatter launcher is a tiny standalone C daemon (not part of the
+# CMake target). Build it here too so install-launcher.sh has its binary.
+# $CC carries flags (mcpu, sysroot, …) so it must stay UNquoted.
+# shellcheck disable=SC2086
+$CC -O2 -o tools/chatter-launcher tools/chatter_launcher.c
+echo "built: tools/chatter-launcher"