fix(install): Makefile uses go install to match docs (#851)

* fix(install): use go install to match docs

Makefile install target now uses 'go install' instead of cp to
~/.local/bin, aligning with documented installation method and
GOPATH/GOBIN conventions.

Closes: hq-93c
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix(beads): set BEADS_DIR for config

* test(config,rig): update startup and bd stubs

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Makefile

@@ -22,11 +22,8 @@ ifeq ($(shell uname),Darwin)
 	@echo "Signed $(BINARY) for macOS"
 endif
 
-install: build
-	cp $(BUILD_DIR)/$(BINARY) ~/.local/bin/$(BINARY)
-ifeq ($(shell uname),Darwin)
-	@codesign -s - -f ~/.local/bin/$(BINARY) 2>/dev/null || true
-endif
+install: generate
+	go install -ldflags "$(LDFLAGS)" ./cmd/gt
 
 clean:
 	rm -f $(BUILD_DIR)/$(BINARY)