fix(app): apply chat-title metadata that raced session-key init (#1251)

The update-session handler dropped the metadata update carrying the chat
title when session encryption wasn't registered yet — a window widened by
the #1242 lazy-load change. Commit 93fec60f fixed the same startup race
for sendMessage and new-message but not this branch, so every chat stayed
on "New chat" (dup #1267, confirmed on iOS).

Mirror that fix here: await the sessions sync queue and re-check both the
stored session and its encryption before giving up.

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Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>