Edit the transcript in the overlay before it's pasted

[janakirampuli]

Today the transcript is pasted at the cursor the instant transcription finishes. When the model mishears something (names, technical terms, a dropped word), the only option is to hunt the mistake down in the target app afterwards — which is clumsy in chat inputs, terminals, and form fields.

Proposal: an opt-in setting (Edit Before Paste, default off) that turns the overlay's transcript panel into a quick editor when transcription completes, instead of pasting immediately:

• The transcript appears in the same overlay panel as an editable text box, with the caret at the end.
• Enter pastes the (corrected) text at the cursor in the target app; Esc discards it.
• Pressing the transcribe shortcut again while the editor is open dictates more text into the editor at the caret — so you can alternate dictate → fix → dictate, then paste once.
• With the setting off, nothing changes.

This is deliberately manual and offline — it complements the automated post-processing discussed in #168 (one commenter there asked for exactly this: "proper integration of manual correction – not LLM"). It reuses the existing overlay window; the main technical work is temporarily granting the (intentionally non-focusable) overlay keyboard focus during editing and releasing it before the paste keystroke fires.

I have a working implementation on a branch (janakirampuli/Handy#feat/edit-transcript-in-overlay) and I'm happy to open a PR if there's interest.