build: add a Makefile task runner

`go run build` cannot work — Go resolves a bare argument as an import
path, so it looks for a package named "build" in std. Wrap the existing
commands in make targets instead, which gives the `make build` /
`make check` ergonomics without changing the Go interface underneath.

The wrapper earns its keep beyond the aliasing: `make serve` builds and
previews dist/ in one step, `make test` runs exactly what CI runs, and
`make update` fails with a pointer to LOCAL_DEV.md when GITHUB_TOKEN is
unset rather than erroring out mid-run.

Cloudflare keeps calling `go run . -build` directly. Locally make is
convenience; in the build image it would be a dependency relied on for
no benefit.

Makefile

@@ -0,0 +1,65 @@
+# Task runner for the repo. Run `make` on its own to list the targets.
+#
+# These are thin wrappers over the Go tool — `make build` is exactly
+# `go run . -build`. The wrapping earns its keep for the targets Go alone
+# cannot express (serve, test, clean) and for not having to remember which
+# steps need a GITHUB_TOKEN and which do not.
+
+DIST ?= dist
+PORT ?= 8080
+
+# Print the help text when make is run with no target.
+.DEFAULT_GOAL := help
+
+.PHONY: help update build check serve test fmt lint clean
+
+help: ## Show this help
+	@echo "Usage: make <target>"
+	@echo
+	@grep -hE '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) \
+		| awk 'BEGIN {FS = ":.*?## "}; {printf "  \033[36m%-8s\033[0m %s\n", $$1, $$2}'
+	@echo
+	@echo "Only 'update' needs network access and a GITHUB_TOKEN."
+
+update: ## Fetch GitHub and refresh README, history and metadata (needs GITHUB_TOKEN)
+	@[ -n "$$GITHUB_TOKEN" ] || { \
+		echo "GITHUB_TOKEN is not set — see docs/LOCAL_DEV.md for how to get one."; \
+		echo "If you only changed tags, notes or the dashboard, use 'make build' instead."; \
+		exit 1; \
+	}
+	go run .
+
+build: ## Render the site into dist/ from committed data (offline)
+	go run . -build
+
+check: ## Validate data/agents.yml (offline)
+	go run . -check
+
+serve: build ## Build, then preview the dashboard locally (override with PORT=)
+	@command -v python3 >/dev/null || { \
+		echo "python3 not found — serve $(DIST)/ with any static file server instead."; \
+		exit 1; \
+	}
+	@echo "Serving $(DIST)/ at http://localhost:$(PORT) — Ctrl-C to stop"
+	@python3 -m http.server $(PORT) -d $(DIST)
+
+test: ## Run everything CI runs (vet, tests, check, build)
+	go vet ./...
+	go test ./...
+	go run . -check
+	go run . -build
+
+fmt: ## Format the Go sources
+	gofmt -w .
+
+lint: ## Run golangci-lint if it is installed
+	@command -v golangci-lint >/dev/null || { \
+		echo "golangci-lint not installed — CI runs it regardless."; \
+		echo "Install: https://golangci-lint.run/welcome/install/"; \
+		exit 1; \
+	}
+	golangci-lint run
+
+clean: ## Remove build output
+	rm -rf $(DIST)
+	rm -f awesome-ai-dev-tools