Tighten catalog entry schema after divergence sweep

[piersdd]

Summary

• normalize all tool entries with explicit plugin types, canonical author types, and array-only service metadata
• tighten catalog-entry validation for type, tier, author_type, services, and documented nullable contract/repository escapes
• retarget make validate to the catalog-entry schema and fail fast
• add regression coverage for all formerly accepted divergent shapes

Residual divergent entries

• blender-mcp and youtube-mcp-server retain contract: null because no canonical contract maps their semantics
• xbox-openxbl-mcp retains repository: null because no verified source repository exists; recommend an operator decide remove-vs-keep separately
• linear-mcp and slack-mcp use repository: null because they are vendor-hosted remote MCPs with no verified source repository in the entry metadata

Additional corpus fixes

• apple-docs-mcp and mcp-nixos now declare tier: community, matching their existing community author classification

Verification

• node --test scripts/catalog-entry.schema.test.js
• node --test scripts/build-catalog.test.js scripts/build-catalog.non-conformance.test.js scripts/domain-scope.test.js
• npm test (194 passed, 15 skipped, 0 failed)
• make validate (59 entries passed)
• node scripts/build-catalog.js (59 plugins built; isolated worktree had no sibling stallari-packs checkout)

Closes #36