feat: add blas/ext/base/ndarray/dapx

[ujjwalv01]

Resolves a part of #14404

Description

What is the purpose of this pull request?

This pull request:

• Implements the ndarray API wrapper for @stdlib/blas/ext/base/dapx (adds a scalar constant to each element in a one-dimensional double-precision floating-point ndarray).
• Ensures consistency with the canonical scalar-operation examples and tests used across the @stdlib/blas/ext/base packages.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: add ndarray interface variants for missing modules in @stdlib/blas/ext/base #14404

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

If you answered "yes" to using AI assistance, please provide a short disclosure indicating how you used AI assistance. This helps reviewers determine how much scrutiny to apply when reviewing your contribution. Example disclosures: "This PR was written primarily by Claude Code." or "I consulted ChatGPT to understand the codebase, but the proposed changes were fully authored manually by myself.".

I used an AI assistant to research existing ndarray packages to ensure consistency with canonical example arrays (e.g., [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] for scalar operations) and to help scaffold the tests and benchmarks. All changes were manually verified and aligned with the blas/ext/base/dapx reference tests.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
blas/ext/base/ndarray/dapx	$\\color{green}121/121$ $\\color{green}+0.00\\%$	$\\color{green}3/3$ $\\color{green}+0.00\\%$	$\\color{green}1/1$ $\\color{green}+0.00\\%$	$\\color{green}121/121$ $\\color{green}+0.00\\%$

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