#433 Direct execution @type prefix fails for repo-local extension model types

Description

The swamp model @<type> method run direct execution syntax unconditionally prepends @ to the type name before looking it up in the type registry. This works for published extensions (whose types are registered as @collective/name) but fails for repo-local extension models whose types are registered without the @ prefix (e.g. sandbox/coder-server).

The help text documents this as: "With @type prefix, auto-creates the definition if needed" — but the auto-creation also fails because the lookup uses the @-prefixed name that doesn't match any registered type.

Steps to Reproduce

1. Create a repo-local extension model in extensions/models/ with a type like sandbox/coder-server
2. Verify it loads: swamp model type search coder --json shows sandbox/coder-server
3. Attempt direct execution: swamp model @sandbox/coder-server method run status my-server

Expected Behavior

Direct execution should resolve sandbox/coder-server from the local type registry and auto-create a model instance, then run the method — the same behavior published extensions get with @collective/name.

Actual Behavior

FTL error Error: "Unknown model type: @sandbox/coder-server"

The @ is prepended to the type string, producing @sandbox/coder-server which doesn't match the registered type sandbox/coder-server.

Workaround

Create the model instance explicitly first, then use the name-based invocation:

swamp model create sandbox/coder-server coder-server --json
swamp model method run coder-server status

Suggested Fix

The direct execution type resolver should strip the @ prefix used as the CLI syntax marker before looking up the type in the registry, or it should attempt lookup both with and without the @ prefix to support both published (@collective/name) and local (namespace/name) types.

Environment

• swamp version: 20260524.004133.0-sha.93c9a4fd
• Platform: linux x86_64 (WSL2)
• Extension location: extensions/models/sandbox-coder-server/mod.ts
• Type registered as: sandbox/coder-server (no @ prefix)