ci: a new test file that never runs is worse than no test file

.github/workflows/test.yml

@@ -48,5 +48,44 @@ jobs:
       - name: Real iroh folder sync and restart
         run: timeout 10m cargo test --locked --test sync_slice -- --test-threads=1
 
+      # The adversarial delete matrix. It was added on 2026-08-25 and NOT added
+      # here, so the two tests that reproduce a file-loss incident ran only on
+      # the author's laptop. That is the same shape as the `--bins` gap above.
+      - name: Adversarial folder sync matrix
+        run: timeout 10m cargo test --locked --test folder_sync -- --test-threads=1
+
       - name: Serial local multi-node daemon slice
         run: timeout 15m cargo test --locked --test local_slice -- --test-threads=1
+
+      # A NEW FILE IN tests/ DOES NOT RUN HERE UNLESS SOMEBODY ADDS A STEP FOR
+      # IT, and forgetting is silent: the suite goes green while the new tests
+      # never execute. That has now happened twice, once for the binary's own
+      # tests and once for the delete matrix.
+      #
+      # So every target must be either RUN above or named below with a reason.
+      # Adding a test file and nothing else fails this step, which is the point.
+      - name: Every test target is accounted for
+        run: |
+          set -euo pipefail
+          # Named here, deliberately not run, with the reason. Shorten this list.
+          not_yet_verified_on_linux="lifecycle pathwatch_slice shell"
+          missing=""
+          for path in tests/*.rs; do
+            target="$(basename "$path" .rs)"
+            if grep -q -- "--test $target" .github/workflows/test.yml; then
+              continue
+            fi
+            case " $not_yet_verified_on_linux " in
+              *" $target "*)
+                echo "known gap, not run here: $target"
+                continue
+                ;;
+            esac
+            missing="$missing $target"
+          done
+          if [ -n "$missing" ]; then
+            echo "these test targets never run in CI:$missing" >&2
+            echo "add a step for each, or name it in not_yet_verified_on_linux with a reason" >&2
+            exit 1
+          fi
+          echo "every tests/*.rs target is run or explicitly accounted for"