Improve OpenCode streaming with line-buffered output

Use stdbuf -oL to set line-buffered stdout for OpenCode commands,
ensuring JSON events are flushed immediately after each newline.
This helps reduce output buffering and improves streaming responsiveness.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: gricha

src/chat/host-opencode-handler.ts

@@ -186,15 +186,15 @@ export class HostOpencodeSession {
       await this.loadHistory();
     }
 
-    const args = ['run', '--format', 'json'];
+    const args = ['-oL', 'opencode', 'run', '--format', 'json'];
 
     if (this.sessionId) {
       args.push('--session', this.sessionId);
     }
 
     args.push(userMessage);
 
-    console.log('[host-opencode] Running: opencode', args.join(' '));
+    console.log('[host-opencode] Running: stdbuf', args.join(' '));
 
     this.onMessage({
       type: 'system',
@@ -203,7 +203,7 @@ export class HostOpencodeSession {
     });
 
     try {
-      const proc = Bun.spawn(['opencode', ...args], {
+      const proc = Bun.spawn(['stdbuf', ...args], {
         cwd: this.workDir,
         stdin: 'ignore',
         stdout: 'pipe',

src/chat/opencode-handler.ts

@@ -118,11 +118,14 @@ export class OpencodeSession {
 
     const args = [
       'exec',
+      '-i',
       '-u',
       'workspace',
       '-w',
       this.workDir,
       this.containerName,
+      'stdbuf',
+      '-oL',
       'opencode',
       'run',
       '--format',