fix: widen instance seed/state types in random/streams/randu

[Planeshifter]

Description

What is the purpose of this pull request?

This pull request:

• widens the instance seed and state member types in random/streams/randu to include the MINSTD variants.

The Options interface already permits selecting a MINSTD generator:

name?: 'mt19937' | 'minstd' | 'minstd-shuffle';
seed?: random.PRNGSeedMT19937 | random.PRNGSeedMINSTD;
state?: random.PRNGStateMT19937 | random.PRNGStateMINSTD;

and the stream forwards seed/state from the underlying PRNG (@stdlib/random/base/randu), which selects a MINSTD generator when name is 'minstd'/'minstd-shuffle'. A MINSTD state is an Int32Array (PRNGStateMINSTD), distinct from MT19937's Uint32Array. However, the instance members were typed MT19937-only:

readonly seed: random.PRNGSeedMT19937;          // before
state: random.PRNGStateMT19937;                  // before

so the declared types rejected valid MINSTD shapes. This widens both to match the Options interface and the sibling random/base/randu declaration (which already uses the union):

readonly seed: random.PRNGSeedMT19937 | random.PRNGSeedMINSTD;
state: random.PRNGStateMT19937 | random.PRNGStateMINSTD;

Related Issues

Does this pull request have any related issues?

No.

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

Identified during a TypeScript-declaration audit of the @stdlib/random namespace and verified against lib/main.js, the base/randu factory, and the @stdlib/types/random seed/state definitions.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

AI Assistance

When authoring the changes proposed in this PR, did you use any kind of AI assistance?

• Yes
• No

If you answered "yes" above, how did you use AI assistance?

• Code generation (e.g., when writing an implementation or fixing a bug)
• Test/benchmark generation
• Documentation (including examples)
• Research and understanding

Disclosure

A TypeScript-declaration audit surfaced this issue using Claude Code; the finding was independently verified against the implementation and the base/randu reference, and reviewed by myself before submitting.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
random/streams/randu	$\color{green}768/768$ $\color{green}+100.00\%$	$\color{green}83/83$ $\color{green}+100.00\%$	$\color{green}14/14$ $\color{green}+100.00\%$	$\color{green}768/768$ $\color{green}+100.00\%$

The above coverage report was generated for the changes in this PR.