`printcraft_engine::guard` wraps `catch_unwind` and returns an error message.
- `Session::apply`: edits run on a copy of the document, so a panic leaves it unchanged and is
reported as an error. A panic while refreshing rolls the edit back.
- `Session::open`, `save_bytes`, `save_full_bytes` and `export_data` report a panic as an
open, write or export error.
- `PrintCraftApp::execute`: a command that panics shows a notice, and the app and its documents
keep running.
- The desktop app installs a panic hook that logs every panic to stderr, with a backtrace when
`RUST_BACKTRACE` is set.
Autosave and crash recovery (`RecoveryStore`) were already in place for anything that escapes.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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