Add the clone engine, CLI, tests, CI, and docs

kage renders every page in headless Chrome, snapshots the final
DOM, strips all JavaScript, and localises CSS, images, and fonts
so a site can be browsed offline as a plain folder of files.

The engine is split into small packages:

  urlx      deterministic URL to local-path mapping and scope rules
  sanitize  remove scripts, on* handlers, and javascript: URLs
  asset     rewrite HTML and CSS references, download assets
  browser   headless Chrome pool over the DevTools protocol
  robots    robots.txt matcher
  clone     the orchestrator: a polite resumable breadth-first crawl

The cli package wires a cobra and fang command surface with two
commands, clone and serve. Every pure package has table tests; the
browser and clone packages add Chrome-driven end-to-end tests that
skip when no browser is present or under -short.

CI runs gofmt, vet, build, race tests, golangci-lint, govulncheck,
and a tidy check on Linux and macOS. A goreleaser config fans one
tag out to archives, deb/rpm/apk, a Chromium-bundled GHCR image,
and the package managers. A tago docs site builds to Pages and
Cloudflare.

cmd/kage/main.go

@@ -0,0 +1,18 @@
+// Command kage clones a website into a self-contained offline folder: it renders
+// every page in headless Chrome, strips all JavaScript, and localises the CSS,
+// images, and fonts so the saved copy looks like the live site but runs no code.
+package main
+
+import (
+	"context"
+	"os"
+	"os/signal"
+
+	"github.com/tamnd/kage/cli"
+)
+
+func main() {
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
+	defer stop()
+	os.Exit(cli.Execute(ctx))
+}