feat(strands-py-wasm): add DecoratedTool for host-side Python tools

[pgrayy]

Description

Introduce DecoratedTool and the @tool decorator as the way to register Python callbacks the agent can invoke. Replaces the prior Tool / PydanticTool pair with a single user-facing type.

from strands import Agent, BedrockModel, tool

@tool
def get_weather(city: str) -> str:
    """Return the current weather for a city."""
    return f"It is 72F and sunny in {city}."

agent = Agent(model=BedrockModel(...), tools=[get_weather])

On the guest (strands-wasm/entry.ts), fix mapContentBlock so the toJSON() outer wrappers from SDK content blocks are stripped to match the WIT inner-record shape, and add mapToolResultBlock / mapToolResultContent helpers for tool-result events. Without this, tool-use events trapped the wasm module on the very first model tool call.

Pin pgrayy-wasmtime to the wasmtime-v46.0.7 release wheel so installation no longer requires a git clone with submodule resolution.

Related Issues

#2421
#2374

Documentation PR

N/A

Type of Change

New feature

Testing

• Added tests/test_tools.py::test_decorated_tool_invocation. Registers @tool def get_weather(...), asks the model "What is the weather in Seattle?", awaits agent.invoke_async, and asserts the tool's value reached the final response ("72" in str(result)). Exercises the full host→guest→host round trip: tool registration, model-issued tool call, Python callback execution, result marshaled back to the model, and final assistant response.
• Verified existing tests/test_agent.py::test_stream_async_hello_world continues to pass.
• Manually inspected the model's full final response to confirm the tool's content was incorporated naturally (e.g., "The weather in Seattle is currently 72°F and sunny. It's a nice day!").

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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