[No QA] refactor: OptionRowLHN — Subtitle subcomponent

[mountiny]

Part of

#89946 — OptionRowLHN compound component decomposition

Step

6 of 12 — depends on #89947 (Provider + context interface). Builds on foundation from #89274 (merged).

What

Extract OptionRow.Subtitle into src/components/LHNOptionsList/Subtitle.tsx.

Contains:

• Alternate text display (optionItem.alternateText)
• TextWithEmojiFragment branch for alternate text containing custom emoji mixed with plain text (alternateTextContainsCustomEmojiWithText logic)
• alternateTextStyle derivation (compact vs default)
• Fullstory fsClass application (alternateTextFSClass)
• Reads all required data from RowContext

Why

Alternate text rendering with its emoji branching logic is a self-contained concern distinct from the title line.

Acceptance criteria

• alternateTextContainsCustomEmojiWithText memo and alternateTextStyle derivation live only in Subtitle.tsx
• No visible behavior or style changes

Issue Owner

Current Issue Owner: @DylanDylann