fix: follow origin/HEAD in pre-commit hook

.husky/pre-commit

@@ -1,14 +1,19 @@
 #!/usr/bin/env sh
 # Fallow gate: block commits that introduce new complexity or duplication
-# beyond the frozen baselines in .fallow/. Matches CI's --base argument
-# exactly (origin/main) so audit scopes to the same diff here and in
-# CI; auto-detection can pick a different ref when origin/main is
-# stale or when multiple remotes are configured, giving false-green
-# locally. If origin/main is behind, run `git fetch origin main` first.
-# To lower a baseline, refactor the flagged code and regenerate:
+# beyond the frozen baselines in .fallow/. Mirrors CI's --base selection
+# by following origin/HEAD (the repo's actual default branch), so the
+# hook adapts if the default changes and doesn't silently diverge from
+# the CI step's `github.base_ref || default_branch` fallback.
+# Non-default-target PRs (e.g. a branch targeting staging while origin
+# defaults to main) will diff differently here than CI will — that's
+# inherent to pre-commit since the eventual PR target isn't known yet.
+# If origin/<default> is behind, run `git fetch` first. To lower a
+# baseline, refactor the flagged code and regenerate:
 #   npx fallow health --save-baseline=.fallow/health-baseline.json
 #   npx fallow dupes  --save-baseline=.fallow/dupes-baseline.json
+BASE=$(git symbolic-ref --short refs/remotes/origin/HEAD 2>/dev/null)
+BASE=${BASE:-origin/main}
 npx fallow audit \
   --health-baseline=.fallow/health-baseline.json \
   --dupes-baseline=.fallow/dupes-baseline.json \
-  --base=origin/main
+  --base="$BASE"