docs: document trunk-based workflow with executable examples

[arturcic]

Description

Add a practical guide for the experimental TrunkBased/preview1 preset, including minimal configuration, branch defaults, deployment modes, and worked examples. The examples use the unmodified TrunkBasedConfigurationBuilder and generate four Mermaid diagrams covering direct main commits, release tags, feature/hotfix merges, and commit-message increments.

Link the guide from workflow selection and branching-strategy and configuration references. Restore the #configuration-tool anchor with the history-verified explanation that the init wizard was removed in v6, and direct readers to current YAML configuration guidance. No production version-calculation behavior changes; rebuilding the wizard remains separate in #3900.

Related Issue

Resolves #3915

Motivation and Context

The preset already exists, but has no dedicated guide or verified examples. Its defaults differ from the customized GitFlow Mainline examples, so the new examples assert the actual preset outputs.

How Has This Been Tested?

• All 48 executable documentation cases passed, including the four new trunk-based cases; both documentation-reference tests passed.
• The documentation build verified 17 generated diagram sources and validated all 18 Mermaid diagrams.
• Full BuildDocs completed for the 7.0, 6.8, and 5.12 editions, including rendered-link validation. Ran in a temporary clone containing identical changes because build-root discovery does not support linked worktrees.
• Browser inspection confirmed the guide, sidebar navigation, and all four diagrams render.
• Formatting verification and git diff --check passed; a second snippet regeneration made no changes.
• New guide and edited usage pages passed Markdown lint. The configuration source retains the same eight pre-existing link-definition warnings as the base revision. Shared dark-theme diagram contrast is unchanged.

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing documentation tests passed (the full production test suite was not run).

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[Copilot]

🟢 Approval recommended

The changes are documentation-focused with supporting executable examples, and the updates align with existing docs/test patterns without introducing product behavior changes.

Review details

• Files reviewed: 13/13 changed files
• Comments generated: 0 new
• Review effort level: Lite

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[mergify]

Thank you @arturcic for your contribution!