Add story structure documentation and parallel execution examples

[Copilot]

• New "Story Structure" documentation page (docs/modules/ROOT/pages/story-structure.adoc) covering:
  • Basic story file structure (Description, Meta, Scenario, steps)
  • GivenStories (story-level and scenario-level with filtering/parameterization)
  • ExamplesTable usage at story and scenario levels
  • Lifecycle steps reference
  • Complete story example
• Updated navigation (docs/modules/ROOT/nav.adoc) to include the new page
• Documentation linting passes (spotlessDocumentationCheck)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Improve VIVIDUS documentation</issue_title>
<issue_description>Hi Dear VIVIDUS team,

As a novice VIVIDUS user, I would like to see more examples of VIVIDUS features in the documentation

• description of the story structure: given stories, example tables, etc
• story-level multithreading configuration and examples

Thanks</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Improve VIVIDUS documentation #3893

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[valfirst]

split this PR into 2 separate ones: one for story structure documentation, another one for parallel execution examples

[Copilot]

split this PR into 2 separate ones: one for story structure documentation, another one for parallel execution examples

Reverted the tests-configuration.adoc changes in 6181251. This PR now only contains the story structure documentation. The parallel execution examples can go in a separate PR.

[valfirst]

split this PR into 2 separate ones: one for story structure documentation, another one for parallel execution examples

Reverted the tests-configuration.adoc changes in 6181251. This PR now only contains the story structure documentation. The parallel execution examples can go in a separate PR.

@copilot move the parallel execution examples in a separate PR.

[Copilot]

split this PR into 2 separate ones: one for story structure documentation, another one for parallel execution examples

Reverted the tests-configuration.adoc changes in [6181251](https://g...

I'm unable to create new PRs — I can only make changes within this existing PR branch. Could you or another contributor open a separate PR for the parallel execution examples? The content that was reverted in 6181251 (the tests-configuration.adoc changes adding the "Parallel Story Execution" subsection) can be used as a starting point.