feat(tools): add replace method to ToolRegistry

[Ratish1]

Description

This pull request introduces a replace() method to the ToolRegistry, enabling the dynamic replacement of tool implementations at runtime. This is a feature for supporting zero-downtime updates, fixing tool bugs mid-session, or rolling out performance optimizations without breaking agent execution.

This PR:

• Added a new replace(tool_name, new_tool) method to src/strands/tools/registry.py.
• The method includes validation to prevent replacing a non-existent tool or using a new tool with a mismatched name.
• Updated both the main registry and the dynamic_tools dictionaries to ensure the registry's internal state remains consistent.
• The method's docstring clarifies that the replacement takes effect on the next agent invocation.
• Added unit tests in test_registry.py to validate the success path, error conditions, and state transitions for dynamic tools.

Related Issues

Closes #1131

Documentation PR

N/A

Type of Change

New feature

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• I ran hatch run prepare
• I ran formatters,linters and precommit checks
• I ran unit tests

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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