refactor: Disallow similar tool names in the tool registry

[zastrowm]

Description

Follow-up to #178, where we discussed preventing similar_tool and similar-tool from both being added to the tool registry, to avoid ambiguity in direct-method invocations.

This removes the need for direct-method invocations from checking for similar names, thus that code was removed

Related Issues

#178, #139

Documentation PR

N/A

Type of Change

• Other (please describe): Refactor

Testing

[How have you tested the change?]

• hatch fmt --linter
• hatch fmt --formatter
• hatch test --all
• Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

Checklist

• I have read the CONTRIBUTING document
• I have added 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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