Reconcile Claude platform qualification with current master

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.github/workflows/ci-routing.yml

@@ -215,10 +215,14 @@ jobs:
           echo "runner=$aws_runner" >> "$GITHUB_OUTPUT"
           echo '::notice title=AWS CI routing::Using an ephemeral RunsOn Fleet runner'
 
-      - name: Select stacked PR CI scope
+      - name: Select PR CI scope
         id: scope
         shell: bash
         env:
+          GH_TOKEN: ${{ github.token }}
+          EVENT_NAME: ${{ github.event_name }}
+          EVENT_BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          EVENT_HEAD_SHA: ${{ github.event.pull_request.head.sha }}
           STACK_JSON: ${{ toJSON(github.event.pull_request.stack) }}
           PR_BASE_REF: ${{ github.event.pull_request.base.ref }}
         run: |
@@ -226,17 +230,53 @@ jobs:
 
           full_ci='true'
           reason='ordinary pull request'
+          # True when the PR's own diff is everything it adds to the stack's
+          # base branch: no stack, or the lowest unmerged PR in one. Above
+          # that, the diff omits lower PRs' code that this run must still test.
+          diff_covers_stack='true'
+
+          # Release notes PRs touch only releases/v*.md or releases/beta/v*.md,
+          # which no build, test, or e2e lane reads. The diff is pinned to the
+          # event's base and head SHAs, so a later push cannot change the
+          # decision for this run. Any lookup failure keeps full CI.
+          release_notes_only() {
+            [[ "${EVENT_NAME:-}" == 'pull_request' ]] || return 1
+            [[ "${EVENT_BASE_SHA:-}" =~ ^[0-9a-f]{40}$ ]] || return 1
+            [[ "${EVENT_HEAD_SHA:-}" =~ ^[0-9a-f]{40}$ ]] || return 1
+
+            local comparison
+            comparison="$(gh api \
+              -H 'Accept: application/vnd.github+json' \
+              -H 'X-GitHub-Api-Version: 2022-11-28' \
+              "/repos/paperclipai/paperclip/compare/$EVENT_BASE_SHA...$EVENT_HEAD_SHA" 2>/dev/null)" \
+              || return 1
+
+            # The compare API lists at most 300 files, so a full page may be
+            # truncated. Renames count both the old and the new path.
+            jq -e '
+              (.files | type == "array") and
+              (.files | length > 0 and length < 300) and
+              all(.files[];
+                (.filename | type == "string") and
+                ([.filename, .previous_filename] | map(select(. != null)) |
+                  all(.[]; type == "string" and test("^releases/(beta/)?v[^/]+\\.md$"))))
+            ' <<< "$comparison" >/dev/null 2>&1
+          }
 
           if jq -e 'type == "object"' <<< "$STACK_JSON" >/dev/null 2>&1; then
             stack_position="$(jq -r '.position // empty' <<< "$STACK_JSON")"
             stack_size="$(jq -r '.size // empty' <<< "$STACK_JSON")"
             stack_base_ref="$(jq -r '.base.ref // empty' <<< "$STACK_JSON")"
+            if [[ -z "$stack_base_ref" || "$stack_base_ref" != "$PR_BASE_REF" ]]; then
+              diff_covers_stack='false'
+            fi
 
             if [[ ! "$stack_position" =~ ^[1-9][0-9]*$ ]] ||
                [[ ! "$stack_size" =~ ^[1-9][0-9]*$ ]] ||
                (( stack_position > stack_size )) ||
                [[ -z "$stack_base_ref" ]]; then
               reason='malformed stack metadata; defaulting to full CI'
+              diff_covers_stack='false'
             elif (( stack_position == stack_size )); then
               reason='top pull request in stack'
             elif [[ "$stack_base_ref" == "$PR_BASE_REF" ]]; then
@@ -247,6 +287,12 @@ jobs:
             fi
           fi
 
+          if [[ "$full_ci" == 'true' && "$diff_covers_stack" == 'true' ]] &&
+             release_notes_only; then
+            full_ci='false'
+            reason='release notes only'
+          fi
+
           echo "full_ci=$full_ci" >> "$GITHUB_OUTPUT"
-          echo "::notice title=Stacked PR CI scope::$reason; full_ci=$full_ci"
+          echo "::notice title=PR CI scope::$reason; full_ci=$full_ci"