* Support Date instance lowering
- Lower read-only Date values and constructors through the C and LLVM backends.
- Add portable calendar helpers, differential coverage, and documented surface contracts.
- Fence unsupported mutation, identity, locale, and component-constructor forms.
Co-authored-by: sensei-woo <sensei-woo@users.noreply.github.com>
* Fix Date exception and timezone semantics
* fix: harden Date lowering edge cases
* fix Date lowering edge cases
* Fix Date union fences and offset clipping
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Co-authored-by: sensei-woo <sensei-woo@users.noreply.github.com>
