refactor(stats/incr/mrmse): add stats/incr/nanmrmse

[jsndz]

---

type: pre_commit_static_analysis_report
description: Results of running static analysis checks when committing changes. report:

• task: lint_filenames status: passed
• task: lint_editorconfig status: passed
• task: lint_markdown status: passed
• task: lint_package_json status: passed
• task: lint_repl_help status: passed
• task: lint_javascript_src status: passed
• task: lint_javascript_cli status: na
• task: lint_javascript_examples status: passed
• task: lint_javascript_tests status: passed
• task: lint_javascript_benchmarks status: passed
• task: lint_python status: na
• task: lint_r status: na
• task: lint_c_src status: na
• task: lint_c_examples status: na
• task: lint_c_benchmarks status: na
• task: lint_c_tests_fixtures status: na
• task: lint_shell status: na
• task: lint_typescript_declarations status: passed
• task: lint_typescript_tests status: passed
• task: lint_license_headers status: passed ---

Resolves #5606

Description

What is the purpose of this pull request?

This pull request:

• Adds a new package @stdlib/stats/incr/nanmrmse.
• Implements an incremental moving root mean square error calculation with special handling for NaN values.
• Ensures that NaN values do not propagate through the accumulated value, maintaining valid computations over a sliding window.

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves [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.

---

@stdlib-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/incr/nanmrmse	$\color{green}143/143$ $\color{green}+100.00\%$	$\color{green}8/8$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}143/143$ $\color{green}+100.00\%$

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