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/deploy-and-run.sh

@@ -0,0 +1,51 @@
+#!/usr/bin/env bash
+# Deploy the chatter binary to the tablet and run it on the e-paper display.
+#
+# Usage: scripts/deploy-and-run.sh [path-to-binary]
+#   default binary: build/chatter
+#
+# Requires: `ssh chatter` working (see doc/tablet_access.md).
+#
+# IMPORTANT lessons baked in here:
+#  * The e-paper framebuffer is a singleton guarded by an flock
+#    (/tmp/epframebuffer.lock). Only ONE process may hold it. A stranded
+#    instance blanks the panel for everyone, so we always stop the previous
+#    chatter unit first.
+#  * Launch as a transient systemd service (systemd-run), NOT an ssh background
+#    job: that detaches cleanly (no held SSH channel) and is stoppable via
+#    `systemctl stop chatter`.
+#  * xochitl owns the display while running, so stop it first (pre-authorized
+#    during development). Run scripts/restore-xochitl.sh to bring it back.
+set -euo pipefail
+cd "$(dirname "$0")/.."
+
+HOST="chatter"
+DEST="/home/root/chatter"   # under /home, NOT the nearly-full rootfs
+
+# Use an explicit binary if given; else a fresh local build; else the prebuilt.
+BIN="${1:-}"
+if [ -z "$BIN" ]; then
+  if [ -f build/chatter ]; then BIN=build/chatter; else BIN=dist/chatter; fi
+fi
+[ -f "$BIN" ] || { echo "binary not found: $BIN (build it, or use the prebuilt dist/chatter)"; exit 1; }
+
+echo ">> stopping any previous chatter + xochitl (release the panel lock)"
+ssh "$HOST" 'systemctl stop chatter 2>/dev/null; systemctl reset-failed chatter 2>/dev/null; systemctl stop xochitl 2>/dev/null; sleep 1'
+
+echo ">> deploying $(basename "$BIN") to $HOST:$DEST"
+ssh "$HOST" "mkdir -p $DEST"
+scp "$BIN" "$HOST:$DEST/"
+
+echo ">> launching chatter as a transient systemd service"
+# LD_LIBRARY_PATH lets the loader resolve libqsgepaper.so (linked for the private
+# EPScreenModeItem type), which lives in the scenegraph plugin dir.
+ssh "$HOST" "systemd-run --unit=chatter --collect \
+  --setenv=QT_QUICK_BACKEND=epaper \
+  --setenv=LD_LIBRARY_PATH=/usr/lib/plugins/scenegraph \
+  --working-directory=$DEST \
+  $DEST/$(basename "$BIN") -platform epaper"
+
+sleep 4
+ssh "$HOST" 'echo "chatter: $(systemctl is-active chatter)"'
+echo ">> logs: ssh chatter 'journalctl -u chatter -f'"
+echo ">> stop:  ssh chatter 'systemctl stop chatter'  (then scripts/restore-xochitl.sh)"