Single-element lists like [1] were being incorrectly unwrapped to "1"
in unstructured content while multi-element lists remained as lists.
This created inconsistent behavior where the structure was lost for
single items.
This fix ensures lists always preserve their structure in unstructured
content regardless of length, making behavior consistent and predictable.
Also removes pretty-printing from JSON serialization for more compact
output across tools, prompts, and resources.
Fixes#1064🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>
Attempting to subclass and monkeypatch was becoming too difficult; inflexibility between low-level types and the requirements of new high-level APIs requires the potential for breaking changes, even if they don't face users.
