feat: orphan pages and merged CMS issues with fix routes

- orphan_page for listed indexable pages no crawled page links to, with
  pages mentioning the title or focus keyphrase as suggestions (D-82)
- CMS-data image_alt and h1_in_content from the content descriptors
  (TopHeading 2 only), stored with the crawl as source cms (D-85, D-50)
- seo-page names Tools edit seo_update_page; every stored issue carries
  a tool or fix code with details.what (P33-38)
- TestIssueMerge (ignored fingerprints survive the next crawl, fixed
  pages lose their issues) and TestStagingCrawl (Pitfall 12)

classes/crawl/orphans.go

@@ -0,0 +1,79 @@
+package crawl
+
+import (
+	"strings"
+
+	"git.golem15.com/golem15/summercms/modules/pact"
+)
+
+// maxSuggestions caps the pages suggested to link to an orphan.
+const maxSuggestions = 10
+
+// minPhrase is the shortest phrase a suggestion matches (in bytes).
+const minPhrase = 3
+
+// checkOrphans reports orphan_page (D-82): an indexable page a sitemap
+// lists that no crawled page links to (the home page is the crawl's
+// entry and never an orphan). Its suggestions are the pages whose main
+// text mentions the orphan's title or its focus keyphrase; the first
+// suggestion's record names the tool that adds the link, else the fix is
+// a link in the site's code.
+func checkOrphans(res *Result, env *Env) []Finding {
+	links := inbound(res)
+	var out []Finding
+	for _, key := range res.Order {
+		p := res.Pages[key]
+		if key == HomePath || !p.InSitemap || !env.indexable(res, p) || len(links[key]) > 0 {
+			continue
+		}
+		rec := env.record(key)
+		var phrases []string
+		add := func(s string) {
+			if s = normal(s); len(s) >= minPhrase {
+				for _, have := range phrases {
+					if have == s {
+						return
+					}
+				}
+				phrases = append(phrases, s)
+			}
+		}
+		if rec != nil {
+			add(rec.Title)
+		}
+		if h1 := p.Facts.H1(); len(h1) > 0 {
+			add(h1[0])
+		}
+		add(p.Facts.Title)
+		if env.Keyphrases != nil {
+			add(env.Keyphrases[key])
+		}
+		var suggestions []map[string]any
+		var first *Record
+		for _, other := range res.Order {
+			if len(suggestions) >= maxSuggestions {
+				break
+			}
+			op := res.Pages[other]
+			if other == key || !op.OK() {
+				continue
+			}
+			text := normal(op.Facts.Text)
+			for _, phrase := range phrases {
+				if strings.Contains(text, phrase) {
+					suggestions = append(suggestions, map[string]any{"url": other, "phrase": phrase})
+					if first == nil {
+						first = env.record(other)
+					}
+					break
+				}
+			}
+		}
+		f := Finding{Kind: KindOrphanPage, URL: key, Locale: locale(rec), Record: first, Details: map[string]any{"count": len(suggestions), "suggestions": suggestions}}
+		if first != nil {
+			f.Content = []string{pact.ContentToolEdit}
+		}
+		out = append(out, f)
+	}
+	return out
+}