v0.8.3

Changes

• omni init prints a plan before it starts (what downloads, what waits for first use) and says why a speech runtime was skipped, instead of "nothing to warm".
• omni doctor has a new runtimes line for the speech, image and video runtimes.
• A missing media runtime is reported once, with the reinstall command (uv tool install --force "omni-api[media]", or brew reinstall omni), instead of "no worker named stt".
• Install hints and README separate the two steps: install the command and its runtimes, then omni init for the models (image and video download on first use or omni init --media).