test(tools): add test coverage for nid_names

[Amirtheshwaran]

What

Add unit test coverage for tools/nid_names.py and register the test suite in CMakeLists.txt.

• Add tools/tests/test_nid_names.py covering:
  • compute_nid: symbol hashing across known PS5 vectors, output length (11), and charset validation.
  • load_db: CSV database parsing, empty/short line handling, and fallback download execution.
  • collect_unknowns: discovery of APS5_EXPORT unknown aliases across PRX sources.
  • collect_real_names: discovery of APS5_VABI implementations and _nid_postfix stripping.
  • main: CLI handling across rename-ready (exit 0), already-implemented (exit 0), MISMATCH (exit 1), and --json serialization.
• Allow main(argv=None) in tools/nid_names.py to receive custom argv for CLI testability.
• Register nid_names in root CMakeLists.txt under BUILD_TESTING (touches the same test registration block as test(tools): add test coverage for check_test_registration #1623).

Tested

Windows 11, Python 3.11:

• python -m unittest discover -s tools/tests -v: 23 tests pass in 1.2s (including all 9 NidNamesTests test cases).
• python tools/check_conventions.py --base origin/main: passed (All conventions checks passed.).

Checklist

• Based on current main; no other open PR implements the same functions
• One topic per PR; follow-ups go in a new PR
• No comments in code except technical debt
• Unimplemented paths throw (NotImplemented_nid_no_patch); silent stubs are listed in TechnicalDebt
• No notes, investigation .md files or images added to the repository (attach them to this PR)
• New third-party code is a submodule built from source
• Generic behaviour, not specific to one title
• Depends on: none
• AI-assisted: yes

[github-actions]

Other open pull requests touch the same code. Merging one will break the other, or both implement the same thing. If this one builds on them, list them in Depends on.

Pull request	Conflicting files (lines on main)	Same exports	Same new files
#1741	CMakeLists.txt L43

[oneandonlydean]

Same as #1623: test coverage for nid_names.py with nothing broken behind it, so closing. #1328 fixes a real bug in the same tool.