Make the CI web-image rebuild its own step; note the shared-workspace image-tag race

AGENTS.md

@@ -89,8 +89,10 @@ them. Revisit only if the stated reason stops holding.
 - **CI docker logins share the runner host's Docker config.** The act_runner is host-mode, so
   `docker login`/`logout` in the workflows mutate one shared `~/.docker/config.json`:
   concurrent jobs can race (one job's logout can 401 another's push — recover by re-running),
-  and tokens sit in that file between login and logout. Accepted for a single-maintainer
+  and tokens sit in that file between login and logout. Same class: concurrent runs share the
-  cadence; serialize with a workflow `concurrency` group if it ever bites.
+  workspace dir, so ci.sh's web-image build races another run's container creation on the
+  `<project>-web` tag. Accepted for a single-maintainer cadence; serialize with a workflow
+  `concurrency` group if it ever bites.
 
 ## Docker only — no host tooling
 

ci.sh

@@ -40,6 +40,12 @@ pkg=$(grep -oE '"@playwright/test": "[0-9.]+"' e2e-tests/package.json | grep -oE
 [ -n "$img" ] && [ "$img" = "$pkg" ] || { echo "Playwright pin mismatch/unreadable: image v$img vs @playwright/test $pkg"; exit 1; }
 echo "ok ($img)"
 
+# Explicit rebuild: without it a stale web image from a previous branch supplies node_modules
+# (the source is bind-mounted but deps are baked in), so a dep bump gets typechecked/tested
+# against the OLD packages. Cheap when deps are unchanged (npm ci layer is cache-keyed).
+step "Build web image"
+docker compose build web
+
 step "Typecheck"
 docker compose run --rm --no-deps web npm run typecheck