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/to-chatter.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+# Switch from the standard interface to Chatter (invoked by the launcher daemon
+# on the multi-finger gesture). Lives on the device at /home/root/chatter/.
+systemctl stop xochitl 2>/dev/null
+systemctl stop chatter 2>/dev/null
+systemctl reset-failed chatter 2>/dev/null
+sleep 1
+systemd-run --unit=chatter --collect \
+  --setenv=QT_QUICK_BACKEND=epaper \
+  --setenv=LD_LIBRARY_PATH=/usr/lib/plugins/scenegraph \
+  --working-directory=/home/root/chatter \
+  /home/root/chatter/chatter -platform epaper