Fix tool uninstall continuing after dangling cleanup

[Genmin]

Summary

• continue processing explicit uv tool uninstall names after removing a dangling tool environment
• preserve the existing dangling-environment behavior for single-name and all-tool uninstall paths
• add an integration regression for uv tool uninstall black ruff when the first tool is missing its receipt

Fixes #19219.

Validation

• cargo fmt --check
• cargo test -p uv --test it tool_uninstall_multiple_names_continues_after_missing_receipt