Decorators

- JS/TS already sorta kinda has decorators, sometimes
- extended placement
- decorators on expressions
- newtypes as decorators
- incl. union newtypes

- queryable
- @if static gating

- @allow, @warn, @deny, @forbid, and @expect tune diagnostics lexically; conditional forms may use static metadata and carry a reason
- @unsafe marks an unsafe operation, while @safe exposes a checked API whose implementation contains unsafe operations
- @derive synthesizes compiler-known interfaces such as Copy, SharedSafe, Clone, Default, comparison, formatting, hashing, and serialization capabilities