refactor: remove unreachable Legacy Components group from DocsSidebar

[hivecommons-hive]

📌 Fixes

Closes #149

---

📝 Summary of Changes

src/components/docs/DocsSidebar.tsx only. Removes the "Legacy Components" sidebar group that could never render on this site:

• LEGACY_PROJECTS (hard-coded []), ALL_PROJECTS (now just PRIMARY_PROJECTS), LEGACY_GROUP_KEY, LEGACY_OVERVIEW_HREF (/docs/legacy-components, not a route)
• renderLegacyGroup — never called; the no-unused-vars warning ESLint reports on main line 467
• the legacyIds block in the initial-collapse effect and the "Keep legacy group collapsed" useEffect, which only mutated navCollapsed for the unrendered group

GENERAL_SECTION_PATH_REGEX is kept — getGeneralSectionSlugFromPath still uses it. Adds changelog.d/changed-remove-legacy-sidebar-group.md.

Verification

• npm run type-check ✅
• npm run lint: 45 → 44 warnings, DocsSidebar.tsx now reports none
• npm test: 78 files / 739 tests pass

Disjoint from #145 (EditPageLink.tsx) and #148 (adds src/__tests__/DocsSidebar.behavior.test.tsx only; no legacy-group references).

---

Filed by scanner agent (ACMM L5 — hold-gated mode). Hold-gated: human review required.

— hive: agent=scanner backend=copilot model=claude-fable-5.1 copilot=1.0.88

[hivecommons-hive]

Important

Held for human review by the hive's ACMM level gate.

This PR was opened by the "scanner" agent while Hive policy required a human checkpoint for that agent. Non-outreach agents are held at ACMM L3–L5; the outreach agent is always held because it publishes project-facing communication.

Hive will automatically remove the hold label once current policy no longer requires a level hold for "scanner". If this is an outreach PR, a human must review it and remove the label.

[kubestellar-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign clubanderson for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[netlify]

✅ Deploy Preview for hivecommons-docs ready!

Name	Link
🔨 Latest commit	70d6c94
🔍 Latest deploy log	https://app.netlify.com/projects/hivecommons-docs/deploys/6abe58c40ba3d700089aebe3
😎 Deploy Preview	https://deploy-preview-150--hivecommons-docs.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[hivecommons-hive]

hive/awaiting-ci: CI pending — sweep will merge when green (after hold is lifted).

---

🐝 Hive Agent: scanner | Instance: hosted-available-oke-11-placeholder-r05x | SHA: unknown

— hive: agent=scanner backend=copilot model=claude-fable-5.1 copilot=1.0.88