feat(api-remotes): enforce the forwardable shape and resolve the invariant companion

The allowlist's satisfies assertion is active again, so a name that is not a
declared event, binds a Scope, or is not one-way fails at the allowlist rather
than on the wire; the owner packages' ./types imports are what give it a real
event vocabulary to judge. The companion's own paths entry lets its test resolve
it from source instead of a built artifact, matching the api-gateway entry.

tsconfig.base.json

@@ -77,6 +77,7 @@
       "@deepseek-ai/dsh-credentials/types": ["./packages/credentials/credentials/src/types.ts"],
       "@deepseek-ai/dsh-settings/types": ["./packages/settings/settings/src/types.ts"],
       "@deepseek-ai/dsh-api-remotes/types": ["./packages/api/remotes/src/types.ts"],
+      "@deepseek-ai/dsh-api-remotes/invariant": ["./packages/api/remotes/src/invariant.ts"],
       "@deepseek-ai/dsh-compact/checkpoint": ["./packages/compact/compact/src/checkpoint.ts"],
       "@deepseek-ai/dsh-compact/types": ["./packages/compact/compact/src/types.ts"],
       "@deepseek-ai/dsh-tools/presentation": ["./packages/core/tools/src/presentation.ts"],