test: add negative name assertions in slot label priority fallback tests

## Summary

When testing label priority fallback logic in slot rendering (e.g., `label` → `localized_name` → `name`), tests should assert **both** that the expected label is rendered *and* that lower-priority names are **not** rendered. This ensures the fallback priority is correctly implemented and prevents regressions.

## Motivation

In PR #10013 (comment: https://github.com/Comfy-Org/ComfyUI_frontend/pull/10013#discussion_r2951861863), reviewer @Myestery suggested adding a negative assertion for `name` when `localized_name` is the expected output. The specific instance in `OutputSlot.test.ts` was fixed in commit 42533ad. However, the same pattern should be audited and applied consistently across all slot/node label rendering tests in the codebase.

## Scope

- Review all existing tests that exercise label priority fallback (e.g., `InputSlot.test.ts`, `OutputSlot.test.ts`, `SubgraphNode.test.ts`, and any similar files).
- For each fallback test case, add a complementary negative assertion (e.g., `expect(wrapper.text()).not.toContain('internal_name')`) to confirm lower-priority values are not leaked into the rendered output.
- Ensure the pattern is applied uniformly: when `label` is set, assert `localized_name` and `name` are absent; when only `localized_name` is set, assert `name` is absent.

## References

- PR: https://github.com/Comfy-Org/ComfyUI_frontend/pull/10013
- Review comment: https://github.com/Comfy-Org/ComfyUI_frontend/pull/10013#discussion_r2951861863
- Requested by: @christian-byrne

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