perf(startup): build the local tool environment in the background and gate its consumers

Runtime creation, MCP launches, Obsidian, native clients and the tool-environment IPC await the initialization promise instead of startup awaiting it before the window path. A failure still fails startup with the same diagnostic.

src/main/local-tool-environment/launch-environment-provider.ts

@@ -3,3 +3,9 @@
  * tool launches. Consumers must only copy the values they explicitly support.
  */
 export type LaunchEnvironmentProvider = () => Readonly<NodeJS.ProcessEnv>
+
+/**
+ * Settles once the launch environment has been built at startup. Consumers that
+ * can run before startup finishes await it before reading the provider.
+ */
+export type LaunchEnvironmentReady = () => Promise<void>