fix(ci): unbreak smoke + htmltest steps post v0.3.0

Three independent CI failures from run 25916500415:

1. Smoke test [linkToSection aria-label] fail on Hugo 0.146 leg.
   The assertion pinned to $post selected via `find ... | head -1`,
   which on 0.146 picked `doc-sach-quan-sat/index.html` — a post with
   zero h2/h3/h4 headings, so zero heading-anchor markup. Rewrite the
   check to scan all built post HTML (same pattern already in use for
   render-link rel). Now reports 13 matches on the demo build.

2. htmltest URLSwap silently never matched. The prior
   `^/tsuki/: /` config (added in d30f50f) used a regex anchor that
   doesn't match htmltest's substring evaluation against minified
   `href=/tsuki/...` attributes. Switch to the unanchored
   `"/tsuki/": /` form. CI has been failing on this since v0.2.0
   despite the "fix" commit; this is the real fix.

3. head.html referenced `/favicon.ico` and `/favicon.svg` but neither
   asset existed in exampleSite/static/. Add a minimal SVG favicon,
   drop the legacy .ico reference (modern browsers fall back to a
   site-rooted /favicon.ico by convention; sites needing one can
   override head.html). Switch the SVG link to `relURL` so the
   `/tsuki/` baseURL prefix is honoured under GitHub Pages subpath
   deploy.

Local validation: all 32 smoke checks green; favicon resolves to
`/tsuki/favicon.svg` and ships in the build artifact.

themes/tsuki/.htmltest.yml

@@ -5,8 +5,13 @@ IgnoreInternalEmptyHash: true
 IgnoreEmptyHref: false
 EnforceHTML5: true
 # Strip the /tsuki/ baseURL prefix so links resolve against exampleSite/public/.
+# htmltest's URLSwap is a regex substring match (not anchored), so the leading
+# "^" used previously silently failed against the minified `href=/tsuki/...`
+# outputs in built HTML — every link reported missing. Quoted plain-prefix form
+# matches whatever position /tsuki/ appears in the href, which for our build is
+# always at the start of relative URLs.
 URLSwap:
-  ^/tsuki/: /
+  "/tsuki/": /
 IgnoreURLs:
   - "^https://giscus.app"
   - "^https://github.com/"

themes/tsuki/exampleSite/static/favicon.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32"><circle cx="16" cy="16" r="14" fill="#4a6fa5"/><circle cx="20" cy="14" r="8" fill="#fbfaf7"/></svg>

themes/tsuki/layouts/_partials/head.html

@@ -49,9 +49,8 @@
   {{- end }}
 {{- end }}
 
-{{/* Favicon */}}
-<link rel="icon" href="/favicon.svg" type="image/svg+xml">
-<link rel="icon" href="/favicon.ico" sizes="32x32">
+{{/* Favicon — SVG only; sites can override head.html to add an .ico fallback */}}
+<link rel="icon" href="{{ "favicon.svg" | relURL }}" type="image/svg+xml">
 
 {{/* Speculation Rules — Chromium prefetch hints; gated, off by default */}}
 {{- $prefetch := site.Params.prefetch -}}

themes/tsuki/scripts/smoke-tests.sh

@@ -70,7 +70,16 @@ assert "BreadcrumbList JSON-LD"    '"@type":"BreadcrumbList"'                "$p
 assert "no breadcrumbs on home"    'class=breadcrumbs'                       "$home" 0
 assert "prev/next nav"             'class=prev-next'                         "$post"
 assert "rel=prev on post"          'rel=prev'                                "$post"
-assert "linkToSection aria-label"  'class=heading-anchor [^>]*aria-label'    "$post"
+# Heading-anchor i18n aria-label must appear somewhere in the build. Pinning to one
+# post is fragile because `$post` is picked by `find | head -1` and short posts
+# without h2/h3/h4 emit no heading-anchor markup.
+anchor_count=$({ grep -roE 'class=heading-anchor [^>]*aria-label' "$public_dir" --include='index.html' || true; } | wc -l)
+if [ "$anchor_count" -lt 1 ]; then
+  echo "::error::FAIL [linkToSection aria-label] expected ≥1 heading-anchor + aria-label across build, got 0"
+  fail=1
+else
+  echo "  ok   [linkToSection aria-label] ${anchor_count} match(es) across $public_dir"
+fi
 assert "no speculationrules by default"  'speculationrules'                  "$home" 0
 
 # llm.txt artifact