Replace generic "Reading"/"Gospel" headings with real incipits

Bible-plan readings now carry a generated bilingual incipit label
(bible-book-incipits.ts) instead of falling through to the UI's generic
"Reading" heading. Gospel pericopes (whether from the user's own plan
or nocturn-readings.ts's proper content) get the same treatment via a
new label field on the 'gospel' ResolvedPart, recovering the book from
the reading's own citation when no raw book code is available.

Updates 3 matins.test.ts assertions that used "no label" as a stand-in
for "this is a bible-plan reading" — no longer true now that these
readings carry a real label, so they now key off the label's shape
(string = patristic attribution, object = generated incipit) instead.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AGjUyhUZJaSjiniEmnLdak

src/ui/hour-view.ts

@@ -49,9 +49,10 @@ function renderCitation(text: ResolvedText, languages: readonly string[]): strin
 function renderLessonLabel(
   label: string | Partial<Record<string, string>> | undefined,
   languages: readonly string[],
+  fallback = 'Reading',
 ): string {
   if (!label) {
-    return '<h3 class="ordo-part-label">Reading</h3>';
+    return `<h3 class="ordo-part-label">${escapeHtml(fallback)}</h3>`;
   }
   if (typeof label === 'string') {
     return `<h3 class="ordo-part-label">${escapeHtml(label)}</h3>`;
@@ -115,7 +116,7 @@ function renderPart(part: ResolvedPart, languages: readonly string[]): string {
     case 'gospel':
       return `
         <section class="ordo-part ordo-part-lesson ordo-part-gospel">
-          <h3 class="ordo-part-label">Gospel</h3>
+          ${renderLessonLabel(part.label, languages, 'Gospel')}
           ${renderCitation(part.text, languages)}
           ${renderColumns(part.text, languages)}
           ${part.source ? `<p class="ordo-part-citation">${escapeHtml(part.source)}</p>` : ''}