feat: preserve JSON structure in MCP tool results

[douglaz]

Summary

This PR enhances MCP tool result handling to preserve JSON structure when tools return structured data, complementing PR #25's smart truncation feature.

Problem

Previously, all tool results were flattened into a simplified format:

{
  "success": true,
  "content": "{\"files\": [...], \"stats\": {...}}"  // JSON as string
}

This lost the structure of complex tool outputs, making them harder to process and analyze.

Solution

The MCP client now:

1. Attempts to parse tool text content as JSON
2. If successful, returns the parsed JSON directly to preserve structure
3. Only falls back to the simplified format for non-JSON content

Example

Before:

{
  "success": true,
  "content": "{\"files\": [\"test.py\", \"main.py\"], \"lines\": 500}"
}

After:

{
  "files": ["test.py", "main.py"],
  "lines": 500
}

Benefits

• Preserves Structure: Complex tool outputs maintain their JSON structure
• Better Integration: Works seamlessly with PR feat: enhance decision tracking beyond PR #23 with smart truncation #25's smart truncation
• Backward Compatible: Non-JSON content still uses the simplified format
• Cleaner Pipeline: Structured data flows cleanly from tools → MCP → decisions

Testing

• JSON content is parsed and preserved
• Non-JSON content falls back to simple format
• Invalid JSON falls back gracefully
• Works with smart truncation from PR feat: enhance decision tracking beyond PR #23 with smart truncation #25

Related

• Builds on PR feat: enhance decision tracking beyond PR #23 with smart truncation #25 (smart truncation for decision tracking)
• Together they ensure structured tool outputs are preserved and intelligently handled throughout the system