feat(ai): add partial JSON parsing for streaming tool calls

- Added partial-json package for parsing incomplete JSON during streaming
- Tool call arguments now contain partially parsed JSON during toolcall_delta events
- Enables progressive UI updates (e.g., showing file paths before content is complete)
- Arguments are always valid objects (minimum empty {}), never undefined
- Full validation still occurs at toolcall_end when arguments are complete
- Updated all providers (Anthropic, OpenAI Completions/Responses) to use parseStreamingJson
- Added comprehensive documentation and examples in README
- Added test to verify arguments are always defined during streaming

packages/ai/package.json

@@ -26,6 +26,7 @@
 		"ajv-formats": "^3.0.1",
 		"chalk": "^5.6.2",
 		"openai": "^5.20.0",
+		"partial-json": "^0.1.7",
 		"zod-to-json-schema": "^3.24.6"
 	},
 	"keywords": [