Summary

Implement structured JSON response format for AI workflow refinement to prevent PARSE_ERROR when AI returns non-JSON responses.

Problem

When AI determines no changes are needed, it sometimes returns Japanese explanation text instead of JSON, causing PARSE_ERROR:

"outputPreview": "現在のワークフローを確認しました。ユーザーのリクエストは..."

Current Behavior

1. User requests refinement in Japanese
2. AI determines no changes needed
3. ❌ AI returns explanation text instead of JSON
4. ❌ Parser fails with PARSE_ERROR

Expected Behavior

1. User requests refinement in Japanese
2. AI determines no changes needed
3. ✅ AI returns structured JSON with status and message
4. ✅ Message displayed in chat UI

Solution

Force AI to always return structured JSON responses:

{
  "status": "success",
  "message": "変更を適用しました",
  "values": {
    "workflow": { /* workflow JSON */ }
  }
}

Changes

File: src/extension/services/refinement-service.ts

• Added AIRefinementResponse and AISubAgentFlowResponse type definitions
• Added parseRefinementResponse() and parseSubAgentFlowResponse() functions
• Updated prompts to require structured JSON format with status, message, and values fields
• Added aiMessage field to result interfaces for chat UI display
• Added raw CLI output to INFO logs for debugging

File: src/extension/commands/workflow-refinement.ts

• Modified to use AI message in chat UI instead of hardcoded translation key

File: src/extension/services/claude-code-service.ts

• Fixed timeout detection to also check exitCode === 143 (128 + SIGTERM)
• nano-spawn may only set exitCode without isTerminated flag

Impact

• AI responses now consistently use structured JSON format
• AI's response message displayed in chat UI for better UX
• Timeout errors correctly reported as TIMEOUT instead of UNKNOWN_ERROR
• No breaking changes to existing workflows

Testing

• Manual E2E testing: Japanese refinement requests
• Manual E2E testing: No-change scenarios return valid JSON
• Manual E2E testing: AI message displayed in chat UI
• Manual E2E testing: Timeout errors reported correctly
• Code quality checks passed (format, lint, check)
• Build successful

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