fix(server): Add explicit JSON response instructions for Cursor prompts

Cursor was writing JSON to files instead of returning it in the response.
Added clear instructions to all Cursor prompts:
1. DO NOT write any files
2. Return ONLY raw JSON in the response
3. No explanations, no markdown, just JSON

Affected routes:
- generate-spec.ts
- generate-features-from-spec.ts
- validate-issue.ts
- generate-suggestions.ts

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

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

apps/server/src/routes/github/routes/validate-issue.ts

@@ -102,9 +102,15 @@ async function runValidation(
       // For Cursor, include the system prompt and schema in the user prompt
       const cursorPrompt = `${ISSUE_VALIDATION_SYSTEM_PROMPT}
 
-You MUST respond with a valid JSON object matching this schema:
+CRITICAL INSTRUCTIONS:
+1. DO NOT write any files. Return the JSON in your response only.
+2. Respond with ONLY a JSON object - no explanations, no markdown, just raw JSON.
+3. The JSON must match this exact schema:
+
 ${JSON.stringify(issueValidationSchema, null, 2)}
 
+Your entire response should be valid JSON starting with { and ending with }. No text before or after.
+
 ${prompt}`;
 
       for await (const msg of provider.executeQuery({