[BUG] Dictation mic button disappears from composer once there's text — regression of the v1.46388.1 fix (macOS 1.49585.0)

v1.46388.1 (2026-09-04) shipped: "Fixed the dictation microphone button disappearing from the chat composer once a message had text, an attached file, or a quoted reply." That behavior is back on 1.49585.0.

Steps to reproduce

1. Open a chat (or Cowork task) with an empty composer — mic icon and its chevron are present.
2. Type any text.
3. Mic icon and chevron disappear; only the send control remains.
4. Select all and delete the text — mic icon returns immediately.

Expected

Mic stays available with text in the composer, so dictation can be appended to already-typed text.

Notes

• Reproduces in both regular chats and Cowork tasks.
• Persists after a full quit and relaunch, so it isn't a stale renderer.
• The chevron beside the mic on this build opens an audio input device picker, not a dictation/voice-mode switch — so this isn't a mode-toggle state issue.

Environment

• macOS, Apple Silicon (arm64)
• Claude desktop 1.49585.0 (41ad1d), built 2026-09-08T05:21:03Z
• Electron 44.2.0

Impact

Breaks the type -> think -> dictate-more workflow entirely; only fallback is macOS system dictation.