improve: README usage/troubleshooting and CI pip cache

[Coding-Dev-Tools]

Automated improvement by dev-engineer.

[github-actions]

🤖 Automated Code Review

✅ Ruff Lint — No issues

⚠️ Ruff Format — Formatting needed

Would reformat: src/configdrift/cli.py
Would reformat: src/configdrift/diff.py
Would reformat: src/configdrift/loader.py
Would reformat: tests/test_cli.py
Would reformat: tests/test_coverage_gaps.py
Would reformat: tests/test_diff.py
Would reformat: tests/test_loader.py
7 files would be reformatted, 2 files already formatted

✅ Secret Detection — Clean

✅ Large Files — Within limits

📊 Diff Stats — 12 file(s) changed

 .github/CODEOWNERS          |   1 -
 .github/workflows/ci.yml    |   6 +-
 README.md                   |  16 +++++
 pyproject.toml              |   2 +-
 src/configdrift/cli.py      | 140 +++++++++-----------------------------------
 src/configdrift/diff.py     |  71 +++++++++-------------
 src/configdrift/loader.py   |  21 ++-----
 tests/conftest.py           |   1 -
 tests/test_cli.py           | 107 ++++++++++-----------------------
 tests/test_coverage_gaps.py |  16 ++---
 tests/test_diff.py          |  56 +++++-------------
 tests/test_loader.py        |   7 +--
 12 files changed, 136 insertions(+), 308 deletions(-)

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

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