fix(adk): support map additionalProperties and bind_param in ToolboxTool

[hsusul]

Summary

• What was wrong: ToolboxTool in toolbox-adk ignored additionalProperties on object/map parameter schemas when building ADK FunctionDeclaration objects (leaving additional_properties=None). Additionally, ToolboxTool lacked the bind_param convenience method available in other packages and threw TypeError when calling bind_params with the keyword argument bound_params.
• What changed: In toolbox_adk.tool.ToolboxTool._build_schema, schema_additional_properties is now populated from param.additionalProperties and passed to google.genai.types.Schema(..., additional_properties=...). Updated bind_params to accept keyword argument bound_params (preserving backward compatibility with bounded_params), and added bind_param.
• What regression coverage was added: test_get_declaration_additional_properties and test_bind_param_and_bind_params_keyword in packages/toolbox-adk/tests/unit/test_tool.py.

Problem

1. When an ADK ToolboxTool was loaded for a tool containing a dictionary/map parameter (such as map<string, string>), _build_schema created a Schema(type=Type.OBJECT) without mapping additionalProperties. As a result, Gemini/ADK function declarations lost value schema constraints for map parameters.
2. ToolboxTool in toolbox-adk diverged from toolbox-core, toolbox-langchain, and toolbox-llamaindex by missing the bind_param singular method and rejecting bound_params as a keyword argument name.

Root cause

1. In toolbox_adk.tool.ToolboxTool._build_schema, schema_additional_properties = None was initialized, but never populated from param.additionalProperties and omitted from the Schema(...) constructor arguments.
2. ToolboxTool in toolbox-adk named its parameter bounded_params instead of bound_params and did not implement bind_param.

Fix

• In packages/toolbox-adk/src/toolbox_adk/tool.py:
  • Extracted param.additionalProperties in _build_schema and recursively converted it when present (or assigned boolean value when bool), passing additional_properties=schema_additional_properties to Schema(...).
  • Updated bind_params to accept bound_params (while preserving bounded_params fallback for backward compatibility).
  • Added bind_param(param_name, param_value) to delegate to bind_params({param_name: param_value}).

Tests

• packages/toolbox-adk/tests/unit/test_tool.py:
  • test_get_declaration_additional_properties: Verifies FunctionDeclaration schema preservation for typed and boolean additionalProperties.
  • test_bind_param_and_bind_params_keyword: Verifies calling bind_param and bind_params(bound_params=...).

Validation

• Executed PYTHONPATH=. /tmp/sdk_env/bin/pytest tests/unit -v inside packages/toolbox-adk: 56 passed.
• Executed black --check ., isort --check ., and MYPYPATH='./src' mypy --cache-dir=.mypy_cache/ -p toolbox_adk in packages/toolbox-adk: all passed with zero errors.

Compatibility

• Fixes ADK schema declarations for map/object parameters.
• Preserves full backward compatibility for bind_params callers while aligning toolbox-adk API with toolbox-core, toolbox-langchain, and toolbox-llamaindex.

Non-goals

• Did not alter core ParameterSchema or transport schema conversion logic.