Two workflow guards had drifted from the code they describe, so
`scripts/ci_guard_checks.sh` failed on a clean tree.
The Flutter release-tag pin moved out of build.yml into the shared
setup-flutter-git composite action, but the checker read that action
from a fixed repository path while its test mutated a workflow fixture.
The mutation could not reach the checker, so the rejection test asserted
against an unmodified run. The checker now resolves the action beside
the workflow it is given, and the test materialises a `.github` tree so
the pin is genuinely exercised.
The script-test roster likewise moved into ci_guard_checks.sh, which
discovers `scripts/test_*.py` by glob; the dispatch guard still expected
each one to be named explicitly in ci_checks.sh and ci.yml. It now reads
that glob and checks both aggregates delegate to the shared roster.
edde746