Move plugins to manifest, pin Docker version, add Makefile

- Add plugins.txt listing all plugins for reproducible installs
- Add Makefile with setup/start/stop/install-plugins targets
- Remove user/plugins/ from git tracking
- Pin Docker image to 1.7.49.5-ls244

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plugins/flex-objects/watch.sh

@@ -1,27 +0,0 @@
-#!/bin/sh
-
-#
-# Configuration
-#
-
-# sass source
-
-SASS_SOURCE_PATH="scss"
-
-# sass options
-SASS_OPTIONS="--source-map=true --style=nested"
-
-# css target
-CSS_TARGET_PATH="css"
-
-#
-# Check prerequisites
-#
-wtfile=$(command -v wt) || { echo "install wellington with 'brew install wellington"; exit 1; }
-
-#
-# Watch folder for changes
-#
-cd -P `pwd`
-$wtfile compile "$SASS_SOURCE_PATH"  -b "$CSS_TARGET_PATH" $SASS_OPTIONS
-$wtfile watch "$SASS_SOURCE_PATH"  -b "$CSS_TARGET_PATH" $SASS_OPTIONS