Keep Orca runtime metadata owned by the active process

[Jinwoo-H]

Summary

• only clear orca-runtime.json when the stopping runtime still owns the published metadata
• stop writing placeholder runtime metadata before the RPC server has a real transport and auth token
• add regression coverage for overlapping runtime owners sharing the same userData directory

Why

Using multiple Orca instances during development could leave a healthy Orca process running without a discoverable orca-runtime.json file. That made orca status report not_running even though the editor was still alive.

Validation

• pnpm exec vitest run src/main/runtime/runtime-metadata.test.ts src/main/runtime/runtime-rpc.test.ts
• pnpm exec tsc --noEmit -p tsconfig.node.json --composite false