[TypeSpec Validation] exclude trailing slash when calculating folder depth

[ckairen]

closes #26549

[openapi-pipeline-app]

Next Steps to Merge

✔️ All automated merging requirements have been met! Refer to step 4 in the PR workflow diagram (even if your PR is for data plane, not ARM).

[openapi-pipeline-app]

Swagger Validation Report

️️✔️BreakingChange succeeded [Detail] [Expand]

There are no breaking changes.

️️✔️Breaking Change(Cross-Version) succeeded [Detail] [Expand]

There are no breaking changes.

️️✔️CredScan succeeded [Detail] [Expand]

There is no credential detected.

️️✔️LintDiff succeeded [Detail] [Expand]

Validation passes for LintDiff.

️️✔️Avocado succeeded [Detail] [Expand]

Validation passes for Avocado.

️️✔️SwaggerAPIView succeeded [Detail] [Expand]

️️✔️TypeSpecAPIView succeeded [Detail] [Expand]

️️✔️ModelValidation succeeded [Detail] [Expand]

Validation passes for ModelValidation.

️️✔️SemanticValidation succeeded [Detail] [Expand]

Validation passes for SemanticValidation.

️️✔️PoliCheck succeeded [Detail] [Expand]

Validation passed for PoliCheck.

️️✔️SpellCheck succeeded [Detail] [Expand]

Validation passes for SpellCheck.

️️✔️Lint(RPaaS) succeeded [Detail] [Expand]

Validation passes for Lint(RPaaS).

️️✔️PR Summary succeeded [Detail] [Expand]

Validation passes for Summary.

️️✔️Automated merging requirements met succeeded [Detail] [Expand]

_{Posted by Swagger Pipeline | How to fix these errors?}

[openapi-pipeline-app]

Swagger Generation Artifacts

️️✔️ApiDocPreview succeeded [Detail] [Expand]

️️✔️SDK Breaking Change Tracking succeeded [Detail] [Expand]

Breaking Changes Tracking

_{Posted by Swagger Pipeline | How to fix these errors?}

[openapi-pipeline-app]

PR validation pipeline restarted successfully. If there is ApiView generated, it will be updated in this comment.

[mikeharder]

Please add a unit test

[ckairen]

Please add a unit test

This unit test will be built on top of the unit test in this pr #26721

blocked until that pr is merged