feat: add tags support to tools for A2A AgentCard skill metadata

[anuyog1004]

Description

Adds support for tags to tools, enabling them to be populated in the A2A AgentCard skill metadata.

Related Issues

Resolves #1261

Documentation PR

N/A. This is an additive feature to the existing @tool decorator. Usage is demonstrated in the PR description.

Type of Change

Bug fix

Testing

How have you tested the change?

• All existing tests pass (1877 tests)
• Added 4 new tests covering:
  • Tool decorator with tags
  • Tool decorator without tags (backward compatibility)
  • Tool decorator with multiple tags
  • A2A server tags propagation
• Ran hatch fmt --formatter and hatch fmt --linter - all checks passed
• Ran hatch test - all tests passed
• 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, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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[anuyog1004]

The integration test failures are unrelated to this PR:

• 3 tests timed out (>45s) due to external API latency
• 215 integration tests passed
• All unit tests passed locally (1877 tests)

These specific failing tests:

• test_rate_limit_throttling_integration_no_retries - Tests OpenAI rate limiting behavior
• test_swarm_resume_from_executing_state - Tests multi-agent swarm execution
• test_swarm_execution_with_string - Tests swarm with string inputs

The changes in this PR only add a tags field to tools and don't modify any integration test behavior.