build: add install-daemon Makefile target for local dev workflow

After make build, run `make install-daemon` to replace the downloaded release
daemon with the locally-built binary. This ensures mxcli uses current dev-branch
code (including unfixed regressions or new features) during local development
and golden rebuilds, rather than the latest release from GitHub.

The target stops any running daemon process before copying, then reports the
installed version for verification.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: engalar

Makefile

@@ -51,12 +51,26 @@ TEST_PARALLEL ?= $(_85PCT)
 # Hard ceiling on how long the full test suite may run.
 TEST_TIMEOUT ?= 180s
 
-.PHONY: build build-debug release clean test _test-inner test-mdl report report-bench report-reset-baseline bench-baseline grammar sync-skills sync-commands sync-lint-rules sync-changelog sync-examples sync-all docs documentation docs-site docs-serve source-tree sbom sbom-report lint lint-go fmt vet update-helpdesk-golden test-helpdesk-regression setup
+.PHONY: build build-debug release clean test _test-inner test-mdl report report-bench report-reset-baseline bench-baseline grammar sync-skills sync-commands sync-lint-rules sync-changelog sync-examples sync-all docs documentation docs-site docs-serve source-tree sbom sbom-report lint lint-go fmt vet update-helpdesk-golden test-helpdesk-regression setup install-daemon
 
 setup:
 	git config core.hooksPath .githooks
 	@echo "Git hooks configured. Pre-commit unit tests enabled."
 
+# Install the locally-built daemon over the downloaded release binary.
+# Ensures mxcli uses the current dev-branch code during local development.
+# Windows: stop running daemon first (taskkill may fail if already stopped).
+install-daemon: build
+	@DAEMON_DIR="$$HOME/.mxcli/daemon"; \
+	DAEMON_BIN="$$DAEMON_DIR/mxcli-daemon$(if $(findstring windows,$(shell go env GOOS)),.exe,)"; \
+	if [ -f "$$DAEMON_BIN" ]; then \
+		echo "Stopping running daemon..."; \
+		pkill -f mxcli-daemon 2>/dev/null || powershell.exe -Command "Stop-Process -Name mxcli-daemon -Force -ErrorAction SilentlyContinue" 2>/dev/null || true; \
+		sleep 1; \
+	fi; \
+	cp "$(BUILD_DIR)/$(DAEMON_NAME)$(if $(findstring windows,$(shell go env GOOS)),.exe,)" "$$DAEMON_BIN"; \
+	echo "Installed: $$DAEMON_BIN ($$("$$DAEMON_BIN" --version 2>&1 | head -1))"
+
 # Helper: copy file only if content differs (avoids mtime updates that invalidate go build cache)
 # Usage: $(call copy-if-changed,src,dst)
 define copy-if-changed