Chat mode: allow holding Space to trigger Claude Code's native voice mode #742

In terminal mode, holding Space reaches the pane and starts Claude Code's built-in voice mode (push-to-talk). In chat mode, the composer keeps every key in the browser, so Claude Code never receives the held Space. The only voice option in chat is the app's own dictation (Ctrl+Shift+Space, BYOK OpenAI).

Expected: an opt-in setting so that holding Space in an empty composer forwards the key to the pane. Claude Code's voice mode then starts, as it does in terminal mode. A tap still types a normal space.

Note: Claude Code records from the host's microphone, so this only helps when the browser runs on the same machine as herdr.

Possible implementation

The input message (shared/protocol.ts) already writes raw text to the pane. In Composer.onKeyDown, behind an opt-in setting and only while the composer is empty:

• Hold the first Space keydown. When a repeat keydown arrives, forward the held space and each repeat with sendInput(pane, " ") and preventDefault(). Claude Code sees the same auto-repeat stream as in a real terminal, and the end of the stream is the release.
• On a keyup without a repeat, insert a normal space into the composer.
• The transcript lands in Claude Code's own input line in the pane. Enter in an empty composer sends "\r" to the pane, as pressEnter does in terminal mode. A small preview of the pane's input line above the composer would let the user read the transcript first.

Version: commit 33f72ce.