feat(editor): M1 pdfrx spike + pen/touch capture

Add pdfrx 2.4.4. PenCaptureRegion routes stylus to ink (arena-bypass
via PenCaptureBinding) while touch falls through to pdfrx scroll/zoom.
Spike pane hosts PdfViewer with page-overlay ink at normalized coords +
frame-time HUD; reachable from home screen for on-device testing.
Bench/coordinate harness under integration_test. Generated assets are
gitignored (regenerate via tool/gen_*.dart).

tool/test.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+# tool/test.sh — flutter test wrapper with sqlite3 workaround.
+#
+# WHY THIS EXISTS:
+#   BadNote vendors sqlite3 native binaries under vendor/sqlite3/ (selected via
+#   the pubspec.yaml `hooks.user_defines.sqlite3.source: test-sqlite3` block).
+#   On Linux the vendored file is `vendor/sqlite3/libsqlite3.x64.linux.so`.
+#   Without pointing the dynamic linker at it, `flutter test` either falls back
+#   to a system sqlite3 (wrong version / missing) or tries to download one at
+#   build time (blocked behind the GFW on this machine).
+#
+#   Setting LD_LIBRARY_PATH to the vendor dir tells the linker to prefer the
+#   vendored shared library.  The Flutter toolchain here (3.41.4 / Dart 3.10.8)
+#   does NOT forward proxy env vars to build hooks, so LD_LIBRARY_PATH is the
+#   reliable workaround for local Linux development.
+#
+#   On Windows CI the vendored sqlite3.x64.windows.dll is picked up
+#   automatically by the native-asset build — no wrapper needed there.
+#
+# USAGE:
+#   tool/test.sh                          # run all tests
+#   tool/test.sh test/foo_test.dart       # run a specific test file
+#   tool/test.sh --coverage               # pass any flutter test flags
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(cd "${SCRIPT_DIR}/.." && pwd)"
+
+VENDOR_SQLITE="${PROJECT_ROOT}/vendor/sqlite3"
+
+if [ ! -d "${VENDOR_SQLITE}" ]; then
+  echo "WARNING: vendor/sqlite3/ not found at ${VENDOR_SQLITE}" >&2
+  echo "         Proceeding without LD_LIBRARY_PATH override." >&2
+else
+  export LD_LIBRARY_PATH="${VENDOR_SQLITE}${LD_LIBRARY_PATH:+:${LD_LIBRARY_PATH}}"
+fi
+
+exec flutter test "$@"