visuals: technology marks, area icons, client wall, two diagrams

Phase 7 (AUD-149), cheapest first.

- internal/brand: vendored Simple Icons path data (CC0) for 50 marks, looked up
  by the technology label the content already uses. Inline SVG, 16 px,
  currentColor, no request and no font. tools/gen_brand_icons.sh regenerates it.
- Six hand-drawn area icons replace the two-letter badges in the nav and on the
  landing cards; the evidence index gets a seventh.
- TechChips renders a mark where one exists and plain text where one does not,
  so a missing icon reads as a decision rather than a broken image.
- Client wall: 45 names as one typeface, one size, one grid of equal tiles, and
  the reason for no logo collage written on the page. No mark invented.
- Two diagrams, authored in-repo: homelab topology (platform-network.md) and
  the RAG pipeline (ai-rag-corpus.md), each referenced from the page it explains.
- Content images now carry intrinsic width/height, loading="lazy" and
  decoding="async" at render time; a site test fails the build if an image
  ships without them.
- Topbar is two rows at desktop: the area names plus marks no longer overlap the
  search form (Lighthouse target-size was failing at 1440 px).
- Favicon, so the browser stops requesting a missing /favicon.ico.

Satisfies: logos on every area page, area icons in nav and cards, two diagrams
referenced from their pages, images sized and lazy, Lighthouse >= 95 held.

(cherry picked from commit a473e4738a3751418c2097df2bcf0568fb6d0208)

internal/web/templates/components.templ

@@ -17,6 +17,7 @@ templ Layout(v LayoutView) {
 			<title>{ v.Title }</title>
 			<meta name="description" content={ v.Description }/>
 			<meta name="color-scheme" content="dark"/>
+			<link rel="icon" href="/static/favicon.svg" type="image/svg+xml"/>
 			<link rel="stylesheet" href="/static/site.css"/>
 			<link rel="stylesheet" href="/static/chroma.css"/>
 			<script src="/static/htmx.min.js" defer></script>
@@ -68,7 +69,8 @@ templ Nav(items []NavItem, current string) {
 templ navLinks(items []NavItem, current string) {
 	for _, it := range items {
 		<a href={ templ.SafeURL(it.Href) } class={ navClass(it) } aria-current={ currentAttr(it) }>
-			<span class="nav-gutter" aria-hidden="true">{ it.Gutter }</span>
+			<span class="nav-mark">@AreaIcon(it.Area)
+</span>
 			<span class="nav-title">{ it.Title }</span>
 		</a>
 	}
@@ -76,7 +78,8 @@ templ navLinks(items []NavItem, current string) {
 
 templ evidenceLink(current string) {
 	<a href="/evidence/" class={ navClassFor(current == "evidence") }>
-		<span class="nav-gutter" aria-hidden="true">EV</span>
+		<span class="nav-mark">@AreaIcon("evidence")
+</span>
 		<span class="nav-title">Evidence index</span>
 	</a>
 }
@@ -178,7 +181,8 @@ templ FragmentView(f stage.Fragment) {
 		</header>
 		switch f.Kind {
 			case stage.KindText:
-				<div class="frag-text">@f.Body</div>
+				<div class="frag-text">@f.Body
+</div>
 			case stage.KindCode:
 				if f.Code != nil {
 					<figure class="code">
@@ -263,7 +267,8 @@ templ EvidenceTable(rows []EvidenceRow) {
 templ PillarCard(c PillarCardView) {
 	<article class="pillar">
 		<p class="pillar-kicker">
-			<span class="pillar-gutter" aria-hidden="true">{ c.Area.Gutter }</span>
+			<span class="pillar-mark">@AreaIcon(c.Area.Key)
+</span>
 			if c.Area.Role != "" {
 				<span>{ c.Area.Role }</span>
 			}
@@ -283,11 +288,7 @@ templ PillarCard(c PillarCardView) {
 			</ul>
 		}
 		if len(c.Tech) > 0 {
-			<ul class="tech" aria-label="Technology">
-				for _, t := range c.Tech {
-					<li>{ t }</li>
-				}
-			</ul>
+			@TechChips(c.Tech)
 		}
 		<p class="pillar-foot">
 			<span class="pillar-count">{ strconv.Itoa(c.Pages) } pages</span>