docs(flash-linear-attention): migrate Ascend quick start guard

[Meihan-chen]

Summary

• migrate the validated flash-linear-attention Ascend NPU Quick Start into sources/
• add the project-local executable documentation test and thin reusable-workflow caller
• add the project to the operator-development homepage section and Sphinx navigation

Validation

• python -m unittest tests.flash_linear_attention.test_project_contract tests.flash_linear_attention.test_quick_start_ascend -v
• parsed the Markdown contract with 5 executable commands and 4 expected-output blocks
• actionlint .github/workflows/flash-linear-attention-quick-start.yml
• Sphinx HTML build succeeds; the remaining PyTorch API warning predates this change

The guarded path retains the proven CANN 9.0 / Python 3.11 image, one-NPU runner, 16 GiB shared memory, latest-release checkout, and real GatedDeltaNet forward/backward smoke.

[ascend-robot]

CLA Signature Guide

@Meihan-chen , thanks for your pull request.

The following commit(s) are not associated with a signed Contributor License Agreement (CLA).

Commit	Reason
53cc721f docs(flash-linear-attention): mi...	the email used in the commit is not linked to a signed CLA! please verify that it matches the email you used when signing the CLA.

To sign CLA, click here.

To check if your email is configured correctly, refer to the FAQs.

Once you've signed the CLA or updating your email, please comment /check-cla to revalidate CLA status.

[Meihan-chen]

/check-cla

[ascend-robot]

CLA Signature Guide

@Meihan-chen , thanks for your pull request.

The following commit(s) are not associated with a signed Contributor License Agreement (CLA).

Commit	Reason
53cc721f docs(flash-linear-attention): mi...	the email used in the commit is not linked to a signed CLA! please verify that it matches the email you used when signing the CLA.

To sign CLA, click here.

To check if your email is configured correctly, refer to the FAQs.

Once you've signed the CLA or updating your email, please comment /check-cla to revalidate CLA status.

[Meihan-chen]

/check-cla

[ascend-robot]

CLA Signature Pass

Meihan-chen, thanks for your pull request. All authors of the commits have signed the CLA. 👍