chore: normalize end-of-file newlines to match .editorconfig

[Coding-Dev-Tools]

What

Normalizes end-of-file newlines on five tracked files so they conform to the repository's own declared standards.

• Add missing final newline: AGENTS.md, CONTRIBUTING.md, requirements.txt
• Collapse stray trailing blank line: README.md, .gitignore

Why

• .editorconfig declares insert_final_newline = true for all files.
• The end-of-file-fixer hook in .pre-commit-config.yaml enforces exactly one trailing newline.

These files currently drift from both. The change is whitespace-only — no code or logic changes.

Verification

• ruff check src/ --target-version py310 → All checks passed
• pytest tests/ → 69 passed

Automated hygiene PR from the repo-improver maintenance rotation.

[github-actions]

🤖 Automated Code Review

✅ Ruff Lint — No issues

⚠️ Ruff Format — Formatting needed

Would reformat: src/apiauth/cli.py
Would reformat: src/apiauth/keygen.py
Would reformat: tests/conftest.py
Would reformat: tests/test_cli.py
4 files would be reformatted, 4 files already formatted

✅ Secret Detection — Clean

✅ Large Files — Within limits

📊 Diff Stats — 5 file(s) changed

 .gitignore       | 1 -
 AGENTS.md        | 2 +-
 CONTRIBUTING.md  | 2 +-
 README.md        | 1 -
 requirements.txt | 2 +-
 5 files changed, 3 insertions(+), 5 deletions(-)

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Verdict: ⚠️ Warnings — Lint/format issues found. Recommend fixing before merge.

Automated by Coding-Dev-Tools/.github reusable workflow.