feat: omit empty state inputs

[SandroMaglione]

Summary

• allow state builder .from() calls to omit the constructor input when {} satisfies the selected schema's exact ~type.make.in
• preserve required inputs, compound and parallel selection callbacks, contextual inference, and parallel-region exhaustiveness
• normalize omitted input to {} before the existing deferred schema.makeEffect construction path, so defaults, class identity, and MachineSchemaDecodeError refinement failures are unchanged
• document the shorthand and add runtime plus negative type coverage across initial, local, local.with, branch, full, compound, parallel, atomic, and final builders

Release

Includes a dedicated minor Changesets entry. After this PR merges into main, the existing Changesets release PR #6 can incorporate this API into the same queued release.

Validation

• pnpm check
• 207 runtime tests
• 92 type tests / 378 assertions
• strict packed-consumer validation
• package verification