feat(corpus): make source links visible on search result cards

- a.passage-card__title now shows teal+underline (was ink/no-decoration, undetectable)
- adds "View source ↗" link below each passage excerpt when source_url present

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

corpus.php

@@ -796,8 +796,11 @@ require_once __DIR__ . '/includes/layout.php';
                     : `<span class="passage-card__title">${esc(hit.title || '(Untitled)')}</span>`;
                 const section  = hit.section ? `<span class="passage-section">§ ${esc(hit.section)}</span>` : '';
                 const excerpt  = highlight(hit.excerpt || '', q);
-                const fullText = (hit.full_text || '').trim();
-                const hasMore  = fullText.length > (hit.excerpt || '').length;
+                const fullText  = (hit.full_text || '').trim();
+                const hasMore   = fullText.length > (hit.excerpt || '').length;
+                const sourceLink = hit.source_url
+                    ? `<a href="${esc(hit.source_url)}" target="_blank" rel="noopener" class="passage-source-link">View source ↗</a>`
+                    : '';
 
                 const card = document.createElement('div');
                 card.className = 'passage-card';
@@ -809,6 +812,7 @@ require_once __DIR__ . '/includes/layout.php';
                     </div>
                     ${titleHtml}
                     <p class="passage-card__excerpt">${excerpt}</p>
+                    ${sourceLink}
                     ${hasMore ? '<button class="passage-expand-btn" type="button" aria-expanded="false">Show full passage</button><div class="passage-full-text" hidden></div>' : ''}`;
 
                 if (hasMore) {