[Vedin]

Native constraint characteristics had no dedicated visitor callback, so consumers could miss RELY in view columns, Hive definitions, domains and supplied ASTs. Add default pre/post hooks to Visitor and VisitorMut on the characteristics type, preserving the actual borrowed instance, default continuation and early breaks. Grammar, AST fields and serialization stay unchanged.

Validation: 1,634 all-feature tests pass with zero failures and seven existing ignored tests, including 47 documentation tests. Configured Rust 1.89 all-target/all-feature Clippy and fmt pass. Four new controls cover native containers, borrowed identity versus equal clones, mutable post-break propagation and existing visitors. The test-first inert-hook baseline records one pass and three failures; a subsequent fixture-only lint correction uses returned errors and a type alias without lint allowances.

Base: feat/snowflake-schema-modifiers-20261113 at merged parser 847d4cf. This parser prerequisite does not activate the separate Rustice consumer or retire engine XFAILs. Draft pending independent review and exact-head CI.