Title: [Docs] Define downstream override policy for org defaults
Labels: area:docs, v0.2.0, governance
Summary: Create an explicit policy describing which org-level defaults are mandatory vs optionally overridden by repos.
Acceptance Criteria:
docs/override-policy.md created with sections: Scope, Mandatory vs Optional, Requesting Exceptions, Versioning & Promotion.
Links added in CONTRIBUTING.md and docs/index.md.
Accessibility and link-hygiene pass complete.
Impact/Risk: Without this, downstream repos drift or block adoption.
Dependencies/Links: Part-1 audit.
Owner: Docs
Telemetry: Count downstream repos acknowledging policy (checkbox in PR template).