Docs: `integration` reference missing `catalog` subcommands

[Quratulain-bilal]

Summary

docs/reference/integrations.md documents the integration commands but omits the catalog subcommand group that exists in code. This breaks parity with the extension, preset, and workflow references, all of which document their catalog management equivalents.

Missing commands

Command	Code location
specify integration catalog list	src/specify_cli/__init__.py:2556
specify integration catalog add <url> [--name]	src/specify_cli/__init__.py:2611
specify integration catalog remove <index>	src/specify_cli/__init__.py:2643

The group is registered at src/specify_cli/__init__.py:1277 (integration_app.add_typer(integration_catalog_app, name="catalog")). The word "catalog" does not appear anywhere in docs/reference/integrations.md.

This is separate from #3174, which covers search/info/scaffold but not the catalog subcommands.

Suggested fix

Add a Catalog Management section to docs/reference/integrations.md matching the structure used in workflows.md (list/add/remove plus resolution order). Config file is .specify/integration-catalogs.yml; env override is SPECKIT_INTEGRATION_CATALOG_URL.

---

note: i used an ai assistant to help investigate and write this up.