Make Send transition directly into Steer

[hamzamerzic]

Summary

• switch the active-turn composer from Send directly to Steer as soon as the queued message appears
• keep the same accent action visible while its icon and meaning change, without an opacity-zero replacement frame
• make an immediate Steer tap wait for the exact queue write instead of becoming inert
• preserve Stop for unanswered questions, disconnected chats, and active turns with no queued work

Prior work

This is a follow-up to #282, which removed the visible queued intermediate state for modified-Enter direct steering. Ordinary Send during a live reply still passed through Stop while the queue write settled, and the primary-action reveal animation then hid the replacement briefly. This change covers that separate ordinary-send transition.

Validation

• frontend library suite: 1,989 passed
• frontend hook suite: 63 passed
• production frontend/PWA build passed
• git diff --check passed

[hamzamerzic]

Superseded by the reviewed visual integration in #295, which preserves this change and its authorship. The integration is now moving through the merge queue.