Add per-schema revision tracking to lexicon package

[athlon-misa]

Summary

Add a revision field to each lexicon JSON schema so individual schemas can be versioned independently of the npm package version. This enables finer-grained compatibility tracking as federation grows.

Context

Follow-up from #23. Currently the lexicon package uses SemVer at the package level only. As more PDS implementations appear, per-schema revision tracking will help consumers detect exactly which schemas changed between releases.

Requirements

• Add revision: integer field to each net.openfederation.* lexicon JSON
• Bump revision on each schema change (automated or enforced via CI)
• Include revision info in generated docs
• Document revision policy (when to bump, what constitutes a breaking vs additive change)

[athlon-misa]

Implemented in branch feat/all-open-issues. Added revision: 1 to all 68 lexicon JSON files, CI validation script (npm run lexicon:validate), docs generation update, and revision policy in CLAUDE.md. Commits: ae51c0a, f8783f0.