feat(sdk): add plugin activationScope (app/project)

Manifests can now declare activationScope to defer activation until a
project is focused, instead of always activating at app bootstrap.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/index.ts

@@ -1,4 +1,5 @@
 export type {
+  IdeAPluginActivationScope,
   IdeAPluginCapability,
   IdeAPluginManifest,
   IdeAPluginEngineConstraints,