Previously build_runner compiled separately for each setup() variant
(checkSrc, backendSrc, integrationSrc, etc.) since their differing
source inputs produced distinct Dagger cache keys. CheckMocks also ran
build_runner twice: once inside setup() and again explicitly — and the
second run always compared two freshly-generated outputs, so stale mocks
in the repo were never detected.
Introduce codegenBase() that runs build_runner on the minimal common
source (lib/, test/, assets/, pubspec.*) excluding committed generated
files. All setup() calls now share this single Dagger cache entry, so
build_runner compiles only once per pipeline run instead of once per
source variant.
Fix CheckMocks to start from pubGetLayer() + committed source (including
any stale *.mocks.dart), commit that state as the git baseline, then run
build_runner once. The subsequent git diff now correctly detects stale
mocks in the repository, matching the behaviour of check_mocks_fresh.sh.
Also update Graph() to reflect the new codegenBase node.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
