feat: server log streaming via SSE for desktop log panel

- LogStreamService: singleton that extends ConsoleLogger, captures all
  NestJS log output into an RxJS Subject while preserving stdout
- main.ts: uses LogStreamService.instance as app logger
- supervisor.controller.ts: new @Sse('logs/stream') endpoint pipes
  log entries (timestamp, level, context, message) to connected clients

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/supervisor/supervisor.controller.ts

@@ -1,6 +1,7 @@
 import { Controller, Get, Post, Body, Query, Sse, Logger } from '@nestjs/common';
 import { Observable, filter, map } from 'rxjs';
 import { SupervisorService } from './supervisor.service';
+import { LogStreamService } from '../logging/log-stream.service';
 
 @Controller('api/supervisor')
 export class SupervisorController {
@@ -76,4 +77,14 @@ export class SupervisorController {
             } as MessageEvent)),
         );
     }
+
+    @Sse('logs/stream')
+    streamLogs(): Observable<MessageEvent> {
+        this.logger.log('[SSE] Log stream opened');
+        return LogStreamService.instance.logSubject.pipe(
+            map(entry => ({
+                data: JSON.stringify(entry),
+            } as MessageEvent)),
+        );
+    }
 }