feat(integrations): add neon Stripe catalog provider

[snowmead]

Summary

• Adds the neon Stripe Projects catalog integration family as CatalogResource adapter(s).
• Follows docs/ADDING-A-PROVIDER.md and docs/PROVIDER-WAVES.md.
• Includes gap test + hermetic provision test. OUTPUT_FIELDS provisional until mise run discover.

Test plan

• Gap + hermetic tests in module
• Live mise run discover when provider is linked
• Merge after resolving additive registry.rs conflict with other family PRs

---

Note

Low Risk
Additive integration registration and offline tests; provisional output envelopes may need discover before live use, with no auth or core lifecycle changes.

Overview
Adds the Neon Stripe Projects catalog integration for neon/postgres as a managed CatalogResource (provider = "neon", outputs database_url / host), with registry wiring, catalog gap test, and hermetic provision test. OUTPUT_FIELDS are provisional until mise run discover neon/postgres.

Also extends stackless-provider-sdk with optional/required integer and boolean config helpers for schema-driven adapters, documents a catalog-first / wave landing process (PROVIDER-WAVES.md, DECISIONS.md), and adds scripts/generate_catalog_integrations.py to scaffold remaining deployables without rewriting registry files.

^{Reviewed by Cursor Bugbot for commit 30a9a59. Bugbot is set up for automated code reviews on this repo. Configure here.}

[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 2 potential issues.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 04d5a45. Configure here.}