🧪 [Add tests for JSON parsing and edge cases in stringification]

[Tcode-Motion]

🎯 What: Adding test coverage for empty JSON collections and escaped quotes in stringify, as well as tests for parse_json_value.
📊 Coverage: Empty lists, empty maps, string escaping in keys and values, and parsing of all core JSON types (null, bool, numbers, strings, arrays, objects).
✨ Result: Increased test coverage for std.json module stringification and parsing functionality.

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PR created automatically by Jules for task 6004555163842917381 started by @Tcode-Motion

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[Tcode-Motion]

This branch has conflicts that must be resolved
](https://github.com/Tcode-Motion/techscript/pull/195/conflicts) or the command line to resolve conflicts before continuing.

stdlib/src/json.rs

[google-labs-jules]

This branch has conflicts that must be resolved
](https://github.com/Tcode-Motion/techscript/pull/195/conflicts) or the command line to resolve conflicts before continuing.

stdlib/src/json.rs

I have resolved the merge conflicts in stdlib/src/json.rs by combining the new tests for stringify_value (empty collections and string escaping) with the comprehensive test_parse_json_value implementation from the main branch.