Fix AttributeError: 'dict' object has no attribute 'merge' in BedrockModel

[jsamuel1]

This PR fixes a critical bug in the Bedrock model initialization that occurs when boto_client_config is passed as a dictionary from JSON configuration parsing.

Problem

• When launching Strands with Bedrock configuration, users encounter: AttributeError: 'dict' object has no attribute 'merge'
• The error occurs because the BedrockModel.__init__ method expects boto_client_config to be a BotocoreConfig object, but configuration parsing from JSON creates a plain dictionary
• The code attempts to call .merge() on the dictionary, which doesn't have this method

Solution

• Added type conversion in the instance() function to detect when boto_client_config is a dictionary
• Convert the dictionary to a proper BotocoreConfig object before passing it to BedrockModel
• Added the necessary import for BotocoreConfig from botocore.config

Changes

• File: src/strands_agents_builder/models/bedrock.py
• Added: Import for BotocoreConfig
• Added: Type conversion logic to handle dict → BotocoreConfig conversion

Testing

This fix addresses the root cause by handling the type conversion at the appropriate layer (where configuration is processed before model instantiation) rather than adding workarounds in the core model implementation.