#903 Local extension files (export const extension) are indexed but methods not merged into target types

Description

Local TypeScript files in extensions/models/ that use export const extension are recognized and indexed by swamp doctor extensions (shown as Indexed), but the methods they declare are never merged into their target types.

Steps to Reproduce

1. Create extensions/models/foo.ts with:

   export const extension = {
     type: '@keeb/docker/compose',
     methods: [{ myMethod: { description: '...', arguments: z.object({}), execute: async () => ({}) } }]
   };

2. swamp doctor extensions --verbose shows the file as Indexed
3. swamp model method run <any-compose-model> myMethod → Unknown method 'myMethod'

Affected Files

• extensions/models/docker_compose_deploy.ts — extends @keeb/docker/compose with deploy, tailscaleAuthUrl, etc.
• extensions/models/docker_engine_rocky.ts — extends @keeb/docker/engine
• Any new local extension file (reproduced with a fresh goldpinger extension)

Expected Behavior

Methods from local export const extension files should be merged into the target type at runtime, the same way methods from pulled-extension packages (e.g. @dmc/proxmox's proxmox_vm_extras.ts) are successfully merged into @keeb/proxmox/vm.

Environment

• swamp version: 20260701.000413.0-sha.eaa21300
• Extension source: extensions/models (configured, confirmed via swamp extension source list)
• Trust: swamp, swamp_lord, john, keeb all trusted