Prevent symbol conflicts when using `accessLevel: public` across multiple packages

[markst]

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Describe the problem

When using XCStringsToolPlugin across multiple Swift packages, setting accessLevel: public in just one package's xcstrings-tool-config.yml causes a conflict if other packages also generate a Localizable symbol (even with default internal access level).

The compiler reports:

'Localizable' is ambiguous for type lookup in this context

This happens because one module exports Localizable publicly, while others still generate the same symbol internally — leading to ambiguity when multiple modules are imported into the same target.

Steps to Reproduce

1. Add .xcstrings files to two Swift packages: PackageA and PackageB
2. Set accessLevel: public in PackageA’s config only
3. Leave PackageB with default or internal
4. Import both packages into an app target
5. Use Localizable.someString