build: widen ruff scope, raise coverage floor, pin meshcore-cli

ruff now checks the whole tree in CI and in `make lint` instead of only
modules/ and tests/. scripts/ and the root-level scripts ship to users
too and were going unlinted; the wider scope flags nothing today, which
makes now the cheap time to widen it.

Coverage floor raised 35 to 50 against an actual 53.21%.

meshcore-cli was the only dependency with no version floor. It is still
required — meshcore_cli.next_cmd backs contact and channel operations
with no equivalent in the meshcore library — so it is pinned rather than
dropped, and the reason is recorded next to it.

Removes the dead [tool.pytest.ini_options] block: pytest.ini takes
precedence, so those settings were never in effect and could only drift
from the ones that are.

.github/workflows/test.yml

@@ -70,7 +70,10 @@ jobs:
         run: pip install "ruff==0.15.15"
 
       - name: ruff check — fail on any lint error
-        run: ruff check modules/ tests/
+        # Whole tree, not just modules/ and tests/: scripts/ and the root-level
+        # scripts (meshcore_bot.py, validate_config.py, generate_website.py, …)
+        # ship to users too. Excludes come from pyproject's [tool.ruff].
+        run: ruff check .
 
       - name: Log injection check — fail on new unsanitized logger calls
         run: python scripts/check_log_injection.py