feat: add stats/incr/nanmrmse

[Arjan-P]

Resolves #5606

Description

What is the purpose of this pull request?

This pull request:

• Adds stats/incr/nanmrmse which calculates moving product, ignoring NaN values.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: add incremental accumulators for handling NaN values in stats/incr/* (tracking issue) #5966
• [RFC]: add stats/incr/nanmrmse #5606

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.

No.

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

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/incr/nanmrmse	$\\color{green}154/154$ $\\color{green}+100.00\\%$	$\\color{green}10/10$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}154/154$ $\\color{green}+100.00\\%$

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

[Planeshifter]

⚠️ Issue Reference Review

An automated check found potentially unrelated issue/PR references in this PR:

Reference	Assessment	Reasoning
#5604	suspicious	PR adds stats/incr/nanmrmse, but issue #5604 is the RFC for a different, unrelated package: stats/incr/nanmprod.

Why this matters: GitHub automatically closes issues referenced with
closing keywords (Resolves, Closes, Fixes) when the PR is merged. Incorrect
references can accidentally close unrelated issues.

What to do:

• If the reference is correct, no action needed. This check may produce
  false positives.
• If the reference is incorrect, please update your PR description.

This assessment was generated by an AI model and is informational only.

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Generated by Claude Code