fix: hatch virtual env fix with optional-dependencies normalization

[lizradway]

Description

Our previous hatch<1.16.0 pin (#330) worked around a feature name normalization bug (pypa/hatch#2128), but is not maintainable since virtualenv 21.0.0 broke older hatch versions (pypa/hatch#2193), requiring upgrade to hatch 1.16.5.

This PR resolves both by normalizing our optional-dependencies keys to hyphens (matching hatch's PEP 685 normalization) and upgrading to hatch>=1.16.5. Also widens pytest and pytest-asyncio upper bounds for compat with hatch 1.16.5's test environment. Fully backwards compatible per PEP 685.

Documentation and README can be updated in future to use hyphens now rather than underscores in line with hatch standards (ie. pip install strands-agents-tools[mongodb-memory]), but functionally both operate the same per PEP 685, so maintaining underscores for now to keep changes to a minimum.

Related Issues

pypa/hatch#2193

Documentation PR

n/a

Type of Change

Bug fix

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

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
• My changes generate no new warnings
• Any dependent changes have been merged and published

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