Add email ownership tracker test documentation

[nonggde]

Closes #438

Summary

• repair the folder-local Email Ownership Tracker README and specs placeholders
• add a contributor-facing test plan and review notes
• add synthetic ownership review fixture cases covering owned, needs-owner, transfer-pending, and stale states
• add a zero-dependency Node documentation/fixture contract test

Scope

• only touches tools/v1/team/email-ownership-tracker/
• no app shell, routing, auth, wallet, Stellar, database, inbox, mail rendering, notification, assignment write, or design-system integration
• no live network calls, secrets, production data, persistence, or side effects

Validation

• node --test tools/v1/team/email-ownership-tracker/tests/email-ownership-docs.test.mjs
• npx --yes prettier --check on the changed Email Ownership Tracker files
• git diff --check
• ASCII scan over tools/v1/team/email-ownership-tracker