feat(node-type-registry): centralize missing defaults in registry

[pyramation]

Summary

Adds missing default values to three Authz* node type definitions so that ALL defaults live in the registry as the single source of truth. Previously these defaults were hardcoded in the cpt_* AST builder functions in constructive-db.

Changes:

• AuthzRelatedPeerOwnership: obj_ref_field — add default: 'id' (was hardcoded in cpt_related_peer_ownership)
• AuthzEntityMembership: add sel_field property with default: 'entity_id' (was hardcoded in cpt_membership_by_field)
• AuthzRelatedEntityMembership: add sel_field (default: 'entity_id') and sprt_join_field (default: 'entity_id') (were hardcoded in cpt_membership_by_join)

This is part of centralizing all defaults — after this publishes, the corresponding COALESCE fallbacks in the constructive-db cpt_* functions will be removed.

Review & Testing Checklist for Human

• Verify the default values match the existing COALESCE fallbacks in policy_ast_builders.sql
• After publishing, regenerate the SQL seed in constructive-db and confirm the defaults appear in the seed

Notes

Companion to constructive-db PRs #967 and #970 which implement the node_type_registry table and generic column cloning for issue #767.

Link to Devin session: https://app.devin.ai/sessions/20dbaaa0e6e74599842fbefe33efbc26
Requested by: @pyramation

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring