Add community review etiquette, inclusive language, events, and social media policies

[khaadish]

Summary

Adds four community governance documents, all self-contained inside
Governance/community/. Each is a versioned, self-contained policy with an
owner, review cadence, and change log, consistent with the existing
Governance/ documents.

File	Covers
Governance/community/REVIEW_ETIQUETTE.md	Review tone and expectations, author and reviewer norms, and how disagreement is handled.
Governance/community/INCLUSIVE_LANGUAGE.md	Preferred terms, terms to avoid, and how the guide is enforced.
Governance/community/EVENTS_POLICY.md	How events are proposed and approved, Code of Conduct applicability, and sponsorship rules.
Governance/community/SOCIAL_MEDIA.md	Who may post officially, tone and disclosure rules, and the escalation path for issues.

Scope

• Documentation only. No TypeScript, configuration, schema, or dependency is
  touched.
• All changes live under Governance/community/; nothing outside Governance/
  is modified.
• Governance/ is outside the Jest root and the TypeScript build, so no test,
  build step, or runtime path is affected.

Notes

• Regression tests are not applicable: this is a documentation-only change with
  no executable code.
• Cross-references point at existing documents (CONTRIBUTING.md,
  CODE_OF_CONDUCT.md, policies/, processes/, roles/, compliance/).

Closes #1865
Closes #1866
Closes #1867
Closes #1868

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