## What changed
- Support `canonical_matching=True` in `prefix_rule` and `canonical_matching = true` in managed TOML prefix rules. Apply Unicode canonical caseless matching to every prefix token, including alternatives, while keeping exact matching as the default.
- Match case and canonically equivalent Unicode spellings, such as `bash` and `bAſh`, without resolving executables on the filesystem.
- Preserve managed restrictions when checking absolute-path rule amendments, and enforce applicable `host_executable` path allowlists during basename fallback.
## Testing
Add coverage for case folding, Unicode normalization, token alternatives, exact-match defaults, and host executable allowlists. Extend managed-policy and shell-execution tests to cover canonical matching.
GitOrigin-RevId: c2f79069dc38d55c77028c457b22beb468d5c571