chore: replace hack with tools and remove obsolete artifacts

- Rename hack/ to tools/ for formal naming
- Update plugin development and deployment script references
- Remove obsolete DESIGN/MILESTONE/PLAN docs now superseded by docs/
- Remove abandoned internal/onebot implementation
- Ignore stray local qq binary artifact

tools/plugin-dev/templates/Makefile.tmpl

@@ -0,0 +1,21 @@
+# Build external Go plugin for HomeAgent
+# Usage: make          # build plugin.so
+#        make clean    # remove plugin.so
+#        make package  # build + create .hmap package
+
+PLUGIN_DIR := $(dir $(abspath $(lastword $(MAKEFILE_LIST))))
+PROJECT_ROOT := $(realpath $(PLUGIN_DIR)../..)
+PLUGIN_NAME := $(notdir $(realpath $(PLUGIN_DIR)))
+
+.PHONY: all clean package
+
+all: plugin.so
+
+plugin.so:
+	cd $(PROJECT_ROOT) && go build -buildmode=plugin -o $(PLUGIN_DIR)plugin.so $(PLUGIN_DIR)
+
+clean:
+	rm -f $(PLUGIN_DIR)plugin.so $(PLUGIN_DIR)$(PLUGIN_NAME).hmap
+
+package: plugin.so
+	cd $(PLUGIN_DIR) && zip -r $(PLUGIN_NAME).hmap plugin.json plugin.so