## What changed
- Separate evidence collection from prompt preparation and pass reviewer history, model limits, and image preparation policy through shared `guardian-context` APIs.
- Detect captured images before composition and measure reviewer history tokens only when images and a valid context window require it.
- Share instruction and native-message delivery filtering across budget checks, including restoration of retained evidence after history changes.
GitOrigin-RevId: 65ef53cf0bc22e1bde9abfb7a9ffce65cfab6f1c