Fix custom emoji rendering

[cbl]

Root cause

AccountDisplayName.vue (the emoji-aware renderer) wasn't used consistently. Some call sites went through it; most didn't. Its hardcoded styling also made it awkward to drop into places that wanted different typography — so people interpolated manually and the shortcodes leaked.

Approach

Make the wrong thing hard to reach. One pure helper, reused everywhere.

• utils/customEmojis.ts — new renderCustomEmojis(html, emojis, imgClass?). Pipeline: sanitize → dedupe emojis (first-wins) → substitute → strip unresolved shortcodes. HTML-escapes the alt attribute (fixes a theoretical XSS when a shortcode contains "). Single source of truth.
• AccountDisplayName.vue refactored to minimal API: name, emojis?, class?. Dropped the asLink/href link-wrapper (caller's concern) and hardcoded font classes (caller owns visual style). Uses the shared helper.
• RichText.vue — inline loop deleted, calls the same helper. Public API unchanged.
• Page header pipeline — usePageHeader composable and useNavigationStore (web + mobile) both extended with titleEmojis. MobileHeader, DesktopFeedHeader, AppHeader render the title via renderCustomEmojis + v-html. Callers that set an account-based title (@[acct].vue, @[acct]/[id]/index.vue, messages/[id].vue, messages/new.vue, mobile MessageThread) now pass emojis.

Fixed

• 17 leaky display-name sites swapped to <AccountDisplayName>: ProfileInformation (profile display name), Status.vue x3 (author header, parent-context preview, reblog indicator), StatusQuote, AccountList, ShareStatusForm x2, ChatHeader, MentionList, Take, search.vue, messages/new.vue. Each caller supplies its own class string.
• Profile field name and value (ProfileInformation.vue) — render via helper with account.emojis. extractText still strips HTML first; emojis are substituted on the plain result.
• Poll options (PollDisplay.vue) — option.title rendered via helper with option.emojis (masto.js types put emojis per-option).
• Chat sender name (MessageBubble.vue) — added senderEmojis prop; caller threads it through from the conversation account. Also sharedStatus.authorEmojis for the shared-post preview shape.
• Chat list group names + sender prefix (ChatListItem.vue) — plain-text context, strips unresolved shortcodes before joining.
• Broken image fallbacks (separate but surfaced in the same audit): Avatar.vue and ProfileHeader.vue now hide <img> on @error so the muted-circle / gradient fallback shows cleanly instead of a broken-image icon + alt text.

Supporting fixes from the same audit

• Alt text in the media lightbox switched from always-visible overlay to a compact ALT pill that opens a bottom-sheet dialog (long descriptions no longer cover the image).
• Status.vue vertical rhythm: pt-3 pb-1 when actions render (balances the button's pb-2 tap target), and pt-1 when a Pinned/reblog indicator is present so the label reads as a caption attached to the post.

Tests

• New utils/__tests__/customEmojis.test.ts — 9 cases covering resolved substitution, unresolved strip, timestamp-unaffected, dedupe of duplicate shortcodes, alt-attribute HTML escaping, empty cases, ReDoS-style input, custom img class.

Exports

• renderCustomEmojis and stripUnresolvedEmojiShortcodes re-exported from @repo/ui so app layers can use them for plain-text contexts (nav page titles, aria-announcements, comma-joined group names).