asw-v01: archive deferred content (packs, site, lab, legacy examples)

- 2.1: packs/ -> archive/packs/
- 2.2: site/ -> archive/site/
- 2.3: src/lab/ -> archive/lab/
- 2.4: examples/ -> archive/examples-legacy/ (SSI-based)

archive/site/layouts/partials/meta/seo.html

@@ -0,0 +1,16 @@
+{{- /*
+  partials/meta/seo.html — canonical URL + robots directives
+
+  Outputs:
+    <link rel="canonical">      Always emitted; uses .Permalink (absolute).
+    <meta name="robots">        "noindex, nofollow" on draft/future pages,
+                                "index, follow" otherwise.
+
+  No params required. Works from any page context.
+*/ -}}
+<link rel="canonical" href="{{ .Permalink }}">
+{{- if or .Draft (gt .Date now) }}
+<meta name="robots" content="noindex, nofollow">
+{{- else }}
+<meta name="robots" content="index, follow">
+{{- end }}