ci(mutation): record the templ pre-build as intentional drift

check-template-drift blocks on any deviation from templates/go-app. ci.yml,
release.yml, codeql.yml and container.yml already carry a templ entry;
mutation.yml is the one workflow that never got it, which is why gremlins was
building three packages short.

Signed-off-by: Sebastian Mendel <info@sebastianmendel.de>

Author: CybotTM

.github/template.yaml

@@ -63,5 +63,17 @@ intentional-drift:
     pass. Other go-app consumers without templ-style codegen don't
     need this, hence intentional-drift rather than a template
     change."
+- path: .github/workflows/mutation.yml
+  reason: "Same templ-extraction problem as ci.yml, release.yml, codeql.yml and
+    container.yml — and the one workflow that never got the treatment. gremlins
+    compiles the packages it mutates, so without `templ generate` it cannot
+    build internal/web/templates, internal/web or cmd/ldap-manager. It reports
+    them as `[build failed]`, drops them from the run, and publishes a score
+    computed over the rest while the job stays green: the mutation score never
+    covered the handler, auth and routing layer. Passes `pre-build-cmd`
+    (introduced in netresearch/.github#314, which also makes `[build failed]`
+    fail the job) with the same go.mod-pinned templ CLI invocation ci.yml uses.
+    Other go-app consumers without templ-style codegen don't need this, hence
+    intentional-drift rather than a template change."
 - path: .github/dependabot.yml
   reason: "Opt-in devcontainers ecosystem. The trimmed go-app template (netresearch/.github#166) declares only gomod/github-actions/docker; this repo has a .devcontainer so it self-manages dependabot.yml to keep devcontainers updates. Core blocks are kept in step with the template manually."