Voice mode: add toggle/continuous listening mode alongside push-to-talk

Problem

Voice mode currently only supports push-to-talk (hold Space to record). This creates a frustrating experience for users who rely on voice input specifically because of hand/wrist strain from typing — the very problem voice mode should solve.

Holding Space continuously while speaking is arguably more taxing on the wrist than typing, since it requires sustained pressure rather than brief keystrokes. It also makes it impossible to interleave voice and keyboard input naturally — you can't glance at output, type a quick correction, then keep talking without physically managing the spacebar.

Proposed Solution

Add a toggle mode for voice input — something like:

• /voice --toggle or a separate /talk command
• Press a key once to start listening, press again (or hit Enter) to stop
• Or even better: continuous listening that automatically sends transcribed text when you pause, and lets you type normally in between

The current push-to-talk could remain as the default for users who prefer it. This would just be an additional option.

Why This Matters

Voice input is most useful for people who think and communicate verbally — and who may have physical reasons to minimize keyboard use. The current implementation forces a choice between:

1. Sustained key pressure (worse for wrists than typing)
2. Putting a physical weight on the spacebar (which then blocks normal keyboard use)
3. Not using voice mode at all

A toggle mode would make voice input genuinely hands-free and practical for real workflows where you naturally switch between speaking and typing.