feat(lsphp): emergency build path compiling lsphp from php.net source

For when a PHP security release is out and the LiteSpeed apt repo lags
(2026-10-21: php2shell CVE-2026-109618/-109619 fixed in 8.2.35/8.3.36/
8.4.27/8.5.12, LiteSpeed still on 8.2.34/8.3.35/8.4.26/8.5.11).

Dockerfile.lsphp / Dockerfile.litespeed gain an `lsphp-src` stage that is
idle unless PHP_SRC_VERSION is set; normal builds are unchanged (measured:
module list, file manifest, ldd, ini and dpkg identical to the published
images).

When set (lsphp-src-build.sh):
- tarball sha256 (php.net releases JSON) + OpenPGP signature against the
  committed php.net keyring, signer pinned per branch
- configure flags replayed from the packaged lsphp's own Configure Command
- LiteSpeed's php-litespeed-8.3 SAPI (what the packages actually compile,
  measured) instead of php-src's sapi/litespeed; sha256-pinned and checked
  against the packaged binary's LSAPI_* names
- packaged compiled-in ini defaults reproduced (session.save_path on 8.2/
  8.3) and gated (`php -n` diff)
- ABI gate (lsphp-abi-gate.sh, pahole) before reusing LiteSpeed's packaged
  PECL .so files; regression-tested in Shell-Checks

lsphp-src-overlay.sh swaps only php-src-owned files (decided by dpkg) and
fails the build unless extensions, versions, effective ini and feature
lines match the packaged lsphp under both CLI and litespeed SAPIs.

CI: lsphp-source-emergency.yaml (workflow_dispatch only). build-push.yaml
refuses to overwrite a newer php.net image with an older packaged one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Dockerfile.litespeed

@@ -22,6 +22,26 @@
 ## after FROM for any RUN steps that need it.
 ARG OLS_VERSION=1.8.5
 ARG PHPVER=83
+
+## ---- EMERGENCY ONLY: lsphp compiled from php.net source ----------------------
+## Idle unless PHP_SRC_VERSION is set (then /lsphp-src-out stays empty and the
+## overlay step below is a no-op). Same stage as Dockerfile.lsphp — see there and
+## docs/lsphp-source-emergency.md.
+FROM litespeedtech/openlitespeed:${OLS_VERSION}-lsphp${PHPVER} AS lsphp-src
+ARG PHPVER=83
+ARG CACHE_BUST=
+ARG EXPECT_LSPHP_PKG=
+ARG EXPECT_PHP_VERSION=
+ARG PHP_SRC_VERSION=
+ARG PHP_SRC_SHA256=
+RUN --mount=type=bind,source=scripts,target=/mnt/scripts \
+    --mount=type=bind,source=keys/php-src,target=/usr/local/share/php-src-keys \
+    set -e; \
+    if [ -n "$PHP_SRC_VERSION" ]; then \
+        install -m 0755 /mnt/scripts/lsphp-apt-upgrade.sh /usr/local/sbin/lsphp-apt-upgrade.sh; \
+    fi; \
+    PHPVER="${PHPVER}" bash /mnt/scripts/lsphp-src-build.sh
+
 FROM litespeedtech/openlitespeed:${OLS_VERSION}-lsphp${PHPVER}
 ARG PHPVER=83
 ENV PHPVER=${PHPVER}
@@ -68,6 +88,17 @@ RUN /usr/local/sbin/lsphp-apt-upgrade.sh "${PHPVER}" \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/* /var/cache/apt/archives/*
 
+## EMERGENCY PATH: overlay the php.net lsphp (no-op on normal builds) and prove
+## it has the same extension/feature surface as the packaged one just installed
+## — see scripts/lsphp-src-overlay.sh. Bind mounts: no extra image layer content.
+ARG PHP_SRC_VERSION=
+ARG LSPHP_SOURCE=litespeed-apt
+RUN --mount=type=bind,from=lsphp-src,source=/lsphp-src-out,target=/lsphp-src-out,rw \
+    --mount=type=bind,source=scripts,target=/mnt/scripts \
+    install -m 0644 /mnt/scripts/lsphp-src-probe.php /usr/local/share/lsphp-src-probe.php && \
+    bash /mnt/scripts/lsphp-src-overlay.sh runtime "${PHPVER}" && \
+    rm -f /usr/local/share/lsphp-src-probe.php
+
 ## Composer (matches the wp-cli pattern in the existing CAC Dockerfile —
 ## phar download, no `php install` pipe since lsphp's CLI mode is fine).
 RUN curl -fsSL -o /usr/local/bin/composer https://getcomposer.org/download/latest-stable/composer.phar && \
@@ -111,8 +142,10 @@ RUN echo "15 */12 * * * root /scripts/log-rotate.sh" >> /etc/crontab
 ##   docker buildx imagetools inspect <ref> --format '{{json .Image.Config.Labels}}'
 ## Values come from CI's repo-index lookup and were asserted against the
 ## installed packages by lsphp-apt-upgrade.sh above ("unverified" = local build).
-LABEL org.whp.php-version="${EXPECT_PHP_VERSION:-unverified}" \
+## Emergency (php.net) builds: see the same LABEL block in Dockerfile.lsphp.
+LABEL org.whp.php-version="${PHP_SRC_VERSION:-${EXPECT_PHP_VERSION:-unverified}}" \
       org.whp.lsphp-package-version="${EXPECT_LSPHP_PKG:-unverified}" \
+      org.whp.lsphp-source="${LSPHP_SOURCE}" \
       org.whp.php-flavour="lsphp${PHPVER}"
 
 EXPOSE 80 443