Remove stale Docsify sidebar

[thomhurst]

Closes #3773

Summary

• remove the obsolete active-docs Docsify sidebar
• keep Docusaurus' autogenerated docs/sidebars.ts configuration authoritative
• leave the versioned v3 documentation snapshot unchanged

Validation

• confirmed no _sidebar.md or Docsify reference remains under active docs/docs
• git diff --check passed

[thomhurst]

@claude review

[thomhurst]

CI diagnosis: the docs-specific GitHub Pages deployment passes. Ubuntu/Windows/macOS .NET failures are only current-main RunReportTests.cs:1483-1484 CS0117 references to removed PipelineOptions.PrintLogo / PrintResults. Focused baseline fix #3864 is already running. This PR deletes one stale Docsify file and does not touch .NET; no rerun until main is repaired.

[thomhurst]

The shared RunReportTests regression is fixed on current main by merged PR #3844. Refreshed this branch onto current main for clean CI and review.

[thomhurst]

@codex review

[thomhurst]

@claude review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 👍

Reviewed commit: f5a886f55b

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[claude]

Code review

No issues found. This PR cleanly deletes the stale Docsify docs/docs/_sidebar.md, matching the intent of #3773:

• Confirmed the file has no other references anywhere in the repo (config, docs, or code) — it was dead weight, since Docusaurus already excludes underscore-prefixed files from the docs plugin.
• Confirmed docs/sidebars.ts remains the authoritative, autogenerated sidebar for the active docs.
• Confirmed the versioned v3 snapshot's _sidebar.md was correctly left untouched, per the PR description — versioned snapshots are a frozen historical record and shouldn't be edited to fix issues in the live docs.

Nothing further to flag — this is a safe, minimal, well-scoped deletion.