Run the text-domain check in a container when the runner has no PHP

The first Gitea run failed on `php: command not found`. GitHub's hosted
runners ship PHP; the Gitea runner image does not, and the whole static job
went red on one line after everything else in it had passed.

ci_php() now uses the local php when there is one — a laptop, GitHub's
runners — and a php:8.4-cli container otherwise. The repository goes in over a
tarball and `docker cp` rather than a bind mount, because a Gitea Actions job
runs inside a container talking to the HOST's docker daemon, so a host path
there lands on an empty directory nobody created.

Also: the include scan now says when it found nothing to check instead of
reporting success. Running the suite with a deliberately crippled PATH showed
it printing "0 plugin-relative include(s) checked" and then "green" — a check
passing by checking nothing, which is the same failure the PHP lint step
already guards against.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

ci/lib.sh

@@ -46,6 +46,35 @@ ci_plugin_header() {
     "$(ci_repo_root)/$PLUGIN_MAIN" | head -1 | sed -E 's/[[:space:]]+$//'
 }
 
+# Run one of this repository's PHP scripts.
+#
+# Uses the local php when there is one — a laptop, GitHub's hosted runners —
+# and a container otherwise. The Gitea runner image has no php, and losing a
+# build to "php: command not found" after everything else passed is a silly way
+# to spend an afternoon. Measured: it happened on the very first Gitea run.
+#
+# The repository goes in over a tarball and `docker cp`, never a bind mount: a
+# Gitea Actions job runs inside a container talking to the HOST's docker
+# daemon, so a host path here lands on an empty directory nobody created.
+ci_php() {
+  if command -v php >/dev/null 2>&1; then
+    php "$@"
+    return
+  fi
+
+  local tarball cid code=0
+  tarball=$(mktemp -t wpci-php-XXXXXX.tar)
+  ( cd "$(ci_repo_root)" && git ls-files -z | tar --null -T - -cf "$tarball" )
+
+  cid=$(docker create "php:8.4-cli" sh -c \
+    "mkdir -p /src && tar -xf /tmp/src.tar -C /src && cd /src && exec php $(printf '%q ' "$@")")
+  docker cp "$tarball" "$cid:/tmp/src.tar" >/dev/null
+  docker start -a "$cid" || code=$?
+  docker rm -f "$cid" >/dev/null
+  rm -f "$tarball"
+  return "$code"
+}
+
 ci_step() { printf '\n\033[1m→ %s\033[0m\n' "$*"; }
 ci_fail() { printf '\033[31mFAIL\033[0m %s\n' "$*" >&2; }