#396 Extension decision order should prefer @swamp/community extensions over local types

Problem

The swamp-extension skill's "When to Create a Custom Model" decision order (mirrored in the managed CLAUDE.md rule 1) is:

1. swamp model type search — local/installed types
2. swamp extension search — community/registry extensions
3. extend an existing type
4. build a custom model

Searching local types first under-weights purpose-built registry extensions: an author can anchor on a generic local/installed type (or be tempted by command/shell) before discovering a better-fit official @swamp extension.

Request

Reorder (or reword) the guidance so registry extensions are considered ahead of local types — and, at minimum, prefer @swamp (official) extensions before authoring a custom model. Suggested order:

1. swamp extension search — prefer an existing @swamp/trusted-community extension
2. swamp model type search — built-in/installed type
3. extend an existing type
4. build a custom model (last resort)