feat(hot-runner): implement hot runner protocol with registry, health monitoring, and job dispatch (#791)

Adds persistent Unity editor instance support to reduce build iteration time
by eliminating cold-start overhead. Includes:

- HotRunnerTypes: interfaces for config, status, job request/result, transport
- HotRunnerRegistry: in-memory runner management with file-based persistence
- HotRunnerHealthMonitor: periodic health checks, idle recycling, job-count recycling
- HotRunnerDispatcher: job routing with wait-for-runner, timeout, and output streaming
- HotRunnerService: high-level API integrating registry, health, and dispatch
- 34 unit tests covering registration, filtering, health, dispatch, timeout, fallback
- action.yml inputs for hot runner configuration (7 new inputs)
- Input/BuildParameters integration for hot runner settings
- index.ts wiring with cold-build fallback when hot runner unavailable

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/model/orchestrator/services/hot-runner/index.ts

@@ -0,0 +1,11 @@
+export { HotRunnerService } from './hot-runner-service';
+export { HotRunnerRegistry } from './hot-runner-registry';
+export { HotRunnerHealthMonitor } from './hot-runner-health-monitor';
+export { HotRunnerDispatcher } from './hot-runner-dispatcher';
+export type {
+  HotRunnerConfig,
+  HotRunnerStatus,
+  HotRunnerJobRequest,
+  HotRunnerJobResult,
+  HotRunnerTransport,
+} from './hot-runner-types';