site: cut the template's own labels out of the pages

Point 7 of the page-wording review. The pages no longer show their data
structure as headings, and they no longer explain their own conventions.

- Level 1 is one screen: claim, status badge, three figures, the technology
  row, and one sentence carrying one link. Measured in headless Chrome at
  1440x900: 1404-1845 px tall before, exactly 900 px (no scroll) after, on
  all six area pages.
- DocPage: no kicker line, no visible level label, no "Evidence for this
  page" heading or instruction note, no "Drill-downs" list, no
  "Status <word> - sentence" footer. The artefact table starts at level 2,
  under the heading "Artefacts"; the history timeline is level 2 only.
- Landing page: "Start here" link text gone, "How to read this site" panel
  gone, the footer's status-label explainer gone.
- Content, presentation only, no claim softened: the leading H1 that
  duplicated the page title removed from all 41 documents; level 1 bodies
  reduced to the constraint as ordinary prose plus the way in;
  "**Status: ...**" prefixes removed from the artefact stubs; "## Drill-downs"
  and "## Period and confidence" removed from the level 2 pages, with the
  cross-area links moved into the prose.
- The six level 1 claims are now sentences with a subject, and use commas
  instead of middots. Same facts, no new ones.

Not in this commit: the 35 level 2 and 3 claims still use the compact CV
style. That is a voice decision for Sam, not a wording tidy-up.

make validate: 41 documents, 0 violations. go test ./...: pass.

(cherry picked from commit 03009f80fc7815ad7719412e125df9297a6e653f)

internal/site/site.go

@@ -257,7 +257,6 @@ func (s *Site) Home() templates.HomeView {
 // Doc builds the view for one document at any depth.
 func (s *Site) Doc(d *content.Document) templates.DocView {
 	area, _ := content.AreaByKey(d.Area)
-	levelLabel := templates.LevelLabel(d.Level)
 
 	view := templates.DocView{
 		Layout: s.Layout(LayoutOpts{
@@ -267,16 +266,14 @@ func (s *Site) Doc(d *content.Document) templates.DocView {
 			Crumbs:      s.crumbs(d),
 			Binding:     s.RouteBinding(),
 		}),
-		Doc:        d,
-		AreaTitle:  area.Title,
-		Role:       area.Role,
-		Body:       templates.MarkdownBody(d.HTML),
-		Metrics:    make([]templates.MetricView, 0, len(d.Metrics)),
-		Tech:       d.Tech,
-		Evidence:   s.evidence(d),
-		Backlinks:  s.backlinks(d),
-		SubPages:   s.subPages(d),
-		LevelLabel: levelLabel,
+		Doc:       d,
+		Role:      area.Role,
+		Body:      templates.MarkdownBody(d.HTML),
+		Metrics:   make([]templates.MetricView, 0, len(d.Metrics)),
+		Tech:      d.Tech,
+		Evidence:  s.evidence(d),
+		Backlinks: s.backlinks(d),
+		SubPages:  s.subPages(d),
 	}
 	for _, m := range d.Metrics {
 		view.Metrics = append(view.Metrics, templates.MetricView{Label: m.Label, Value: content.MetricValue(m.Value)})
@@ -334,7 +331,7 @@ func (s *Site) evidence(d *content.Document) []templates.LinkView {
 func (s *Site) backlinks(d *content.Document) []templates.LinkView {
 	out := make([]templates.LinkView, 0, len(d.Backlinks))
 	for _, b := range d.Backlinks {
-		out = append(out, templates.LinkView{Label: b.Title, Href: b.URL, Kind: templates.LevelLabel(b.Level)})
+		out = append(out, templates.LinkView{Label: b.Title, Href: b.URL})
 	}
 	return out
 }