fix: use json-stream-stringify for pretty-printing MCP config files

[Michaelzag]

Summary

This PR fixes Issue #9862 - MCP settings UI removes JSON formatting on save.

Problem

The safeWriteJson() utility was using stream-json's Stringer class which only outputs compact/minified JSON, making configuration files like .roo/mcp.json difficult to read and manually edit after being modified through the UI.

Solution

• Replaced stream-json with json-stream-stringify library which supports streaming pretty-printing via its spaces parameter
• Added a prettyPrint option to the safeWriteJson() function
• Updated all MCP configuration write calls to use { prettyPrint: true }
• Properly handles undefined values by converting them to null for valid JSON serialization (matching the original behavior)

Why json-stream-stringify instead of JSON.stringify?

JSON.stringify() would load the entire object into memory before streaming, defeating the purpose of streaming for large files. json-stream-stringify handles indentation during the streaming process itself, maintaining true O(1) memory usage regardless of file size.

Changes

• src/utils/safeWriteJson.ts: Replaced stream-json with json-stream-stringify, added prettyPrint option
• src/services/mcp/McpHub.ts: Updated all config writes to use { prettyPrint: true }
• src/core/webview/webviewMessageHandler.ts: Updated project MCP settings to use pretty-printing
• src/package.json: Added json-stream-stringify dependency

Testing

• All existing safeWriteJson tests pass
• Manually verified MCP config files maintain formatting after UI modifications

Fixes #9862

---

Important

Switches to json-stream-stringify for streaming pretty-printing of MCP config files, enhancing readability.

• Behavior:
  • Replaces stream-json with json-stream-stringify in safeWriteJson() to support streaming pretty-printing.
  • Adds prettyPrint option to safeWriteJson() for JSON formatting.
  • Updates all MCP config writes in McpHub.ts and webviewMessageHandler.ts to use { prettyPrint: true }.
• Dependencies:
  • Adds json-stream-stringify to package.json dependencies.
• Testing:
  • All existing safeWriteJson tests pass.
  • Manually verified MCP config files maintain formatting after UI modifications.

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[roomote]

Rooviewer   See task on Roo Cloud

Review completed - no issues found. The implementation correctly replaces stream-json with json-stream-stringify to enable pretty-printing while maintaining true streaming efficiency and all existing safety guarantees.

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}