Add new auto builders

[vethman]

Auto builders, deprecation of the hand-written builders, and a large round of fixes

New: auto builders

• CeriosAutoBuilder<T>() and CeriosClassAutoBuilder(Class) — base-class factories that generate a bare-name setter for every property, so hand-written setProperty wrappers are no longer needed. Custom methods mix freely with the generated setters, and the existing compile-time required-property tracking is kept: calling build() before all required properties are set is a compiler error.
• Nested-builder composition — BuilderComposerFromFactory / ClassBuilderComposerFromFactory now accept auto-builder factories, so custom methods can hand callers a preconfigured child builder with full type safety.
• Base types & shared builder logic — shared custom methods can be written once as a base-builder function (constrained on AutoBuilderBase<TBase> / ClassAutoBuilderBase<TBase>) and applied to each concrete auto builder via BuilderExtension, replacing the old generic base-builder-class pattern.
• BuilderWith / ClassBuilderWith — ergonomic types for explicit return-type annotations, and one unified constructor shape new Builder(data, { requiredFields, validators }) for both factories.

Deprecations

• CeriosBuilder and CeriosClassBuilder are deprecated and will be removed in the next major version. See MIGRATION.md for a per-feature before/after guide.
• An all-optional type can now build() immediately — the compile-time gate dissolves when there are no required properties (all four base classes).

Fixes (highlights)

• Builders no longer hand out or freeze their live internal state — build(), buildUnsafe(), buildFrozen(), buildSealed(), and buildPartial() all return proper copies, so mutating a result can no longer corrupt the builder.
• Deep clone preserves Date, Map, Set, RegExp, and class prototypes, and handles circular references.
• Prototype-pollution hardening: __proto__ is rejected as a key/path in all setters and is no longer a generated setter name.
• Proxy edge cases fixed: properties named after inherited members (e.g. hasOwnProperty) can no longer silently invoke the real method, and copy-on-write preserves subclass instance fields, validators, and required fields.
• Validation errors are now a typed CeriosBuilderError with missingFields / validationErrors, and failing validators are identified by index and name.

Packaging

• Published artifacts are now explicit dual CJS/ESM with per-condition type declarations (.d.cts / .d.mts), built with tsdown (was tsup) and validated with @arethetypeswrong/cli in CI. Entry-point imports are unaffected.