ci(repo-ci): scan the full push range for attribution residue (#30)

On `pull_request` the attribution-residue step scans
`origin/<base>..HEAD`. On `push`, `github.base_ref` is empty, so
`AI_RESIDUE_BASE_REF` resolved to a bogus ref and the checker fell back
to scanning only the single HEAD commit.

This widens push-event coverage to `github.event.before..HEAD` (every
commit in the push) and stops re-scanning commits already on the base
branch. The marker-matching logic is unchanged — this only fixes the
commit range on push events. Resolves the spurious failure on the latest
`main` run.

Author: NWarila

.github/workflows/repo-ci.yml

@@ -64,6 +64,10 @@ jobs:
           BASE_REF: ${{ github.base_ref }}
         run: git fetch --no-tags origin "+refs/heads/${BASE_REF}:refs/remotes/origin/${BASE_REF}"
         env:
+          # On pull_request, scan origin/<base>..HEAD (the PR's commits).
+          # On push, github.base_ref is empty, so scan github.event.before..HEAD
+          # (every commit in the push) instead of only HEAD — wider coverage,
+          # and avoids re-scanning commits already on the base branch.
 
   adr-schema:
     name: Validate ADR schema