docs: clarify how to rename a Test-Set

[officialasishkumar]

What has changed?

The Rename Test-Sets section on versioned_docs/version-4.0.0/running-keploy/rename-testcases.md was a single sentence that told users they could rename test-set-0, but didn't explain:

• Why Keploy accepts the rename (folder-based discovery — no test-set- prefix filter).
• Which folder names are reserved (reports, testReports, schema).
• How to reference the renamed Test-Set at replay time (-t / --test-sets).
• That pre-existing report files keep the old Test-Set name.

This PR expands the section to cover all four points, verified against pkg/platform/yaml/yaml.go:ReadSessionIndices in keploy/keploy.

This PR Resolves keploy/keploy#4069

Type of change

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).
• Documentation update (if none of the other choices apply).

How Has This Been Tested?

Prose-only change. Verified locally:

• vale versioned_docs/version-4.0.0/running-keploy/rename-testcases.md — 0 errors on changed lines (filter_mode: diff_context in CI skips the two pre-existing frontmatter/example errors on unchanged lines).
• npx prettier@2.8.8 --check versioned_docs/version-4.0.0/running-keploy/rename-testcases.md — clean.
• No frontmatter, sidebar, or admonition changes, so the Docusaurus build surface is unchanged.

Checklist:

• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.

[Copilot]

Pull request overview

This PR expands the Rename Test-Sets guidance in the v4.0.0 docs to explain how Keploy discovers Test-Set directories, which names are reserved, how to target renamed Test-Sets at replay time, and how renames affect report filenames.

Changes:

• Replaced the single-sentence “rename test-set-0” instruction with a more complete explanation of folder-based discovery.
• Documented reserved directory names to avoid and how to run keploy test against a renamed Test-Set via -t/--test-sets.
• Added a note about how pre-existing report filenames behave across a rename.

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[Copilot]

The path/pattern here is inconsistent with other v4.0.0 docs: keploy/reports/test-run-*/ (with a trailing /) reads like a directory glob, but cli-commands.md documents report files like keploy/reports/test-run-1.yaml and risk-profile-analysis.md references test-run-*-report.yaml. To avoid misleading users, please update this sentence to use the actual report filename pattern (and remove the trailing slash if these are files).

Suggested change

	Report files generated before the rename keep the old Test-Set name in their filenames under `keploy/reports/test-run-*/`. Runs after the rename use the new name.
	Report files generated before the rename keep the old Test-Set name in their filenames under `keploy/reports/test-run-*.yaml`. Runs after the rename use the new name.