* [Chore] CI: Block PRs that drop overall code coverage
Tighten Codecov project status threshold from 1% to 0% so any drop in
overall project coverage relative to the base commit fails the
codecov/project check. target: auto keeps the bar floating with the
codebase, no manual maintenance needed as coverage moves up over time.
* [Chore] CI: Always post Codecov status regardless of CI outcome
Set codecov.require_ci_to_pass: false and codecov.notify.wait_for_ci:
false so Codecov posts the codecov/project and codecov/patch checks as
soon as the expected uploads arrive, instead of withholding them when
unrelated CI jobs fail. The coverage-regression check is independent
of test pass/fail, and CI failures are already enforced by their own
required-status checks.
