v0.4.0 — hands-free lock

Thank you for the feedback that shaped this release. Every fix below came
from a real dictation someone reported.

What changed

• Option+A locks dictation on. Hold Right-Option, tap A, let go; tap
  Option+A again to finish. Speech is split into sentences on ~0.7 s pauses;
  each is cleaned up and committed, and committed text is never corrected
  again, so anything you type yourself stays intact.
• Focus-aware delivery. Switch apps while locked and dictation keeps
  listening; the words are typed the moment the original field has focus
  again, or at the end.
• A fast model for the preview, the accurate one for the text. The
  live preview now runs base.en (about 0.4 s per update, so words appear
  every half second); every committed or final sentence is decoded by
  small.en. Preview corrections are word-based: a comma the preview
  chose differently is left alone rather than retyping the line.
• No more decoder stalls or loops. Whisper's temperature-fallback
  ladder (up to six re-decodes on a chunk cut mid-word, 7 s stalls) is
  off; repeated phrases ("the the the") are cut at the first repeat; the
  preview decoder cannot repeat a trigram; an empty preview never deletes
  anything.
• The app ignores its own keystrokes. Typed words are tagged so the
  hotkey listener no longer mistakes them for Option+A or a language key.
• No double paste. Each dictation owns its typing state and its
  preview loop, and all keystrokes go through one lock, so a quick second
  press while a long dictation is still finalizing can no longer make it
  type the whole section again or interleave stale preview text.
• Long dictations split at a pause. Past the 24 s window the buffer is
  cut at the last short pause instead of mid-word, so no sentence gets a
  spurious full stop in the middle.

Upgrading

cd local-flow && git pull && ./install.sh
launchctl kickstart -k gui/$(id -u)/com.localflow.dictation

The preview model (base.en, about 75 MB) downloads on first use.