CI: retry Yarn Classic dep packing on transient esbuild fetch corruption

Build #78 failed in the compile step while Yarn Classic prepared the
@replit/codemirror-* git deps: fetching esbuild's per-platform binaries
returned truncated tarballs ("the file appears to be corrupt" / missing
.yarn-tarball.tgz). The tmpfs classic cache is fresh each build, so there is no
stale entry to blame and nothing to fall back to — it is a transient download
failure (builds #75-77 passed with an identical Dockerfile).

Wrap both the install and compile steps in a 3-attempt retry loop that wipes
the Yarn Classic cache (/usr/local/share/.cache/yarn) and re-fetches before
giving up, dumping pack.log on final failure. The persistent Berry cache and
YARN_NETWORK_CONCURRENCY=1 are unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server-ce/Dockerfile

@@ -34,10 +34,22 @@ ENV COREPACK_ENABLE_NETWORK=0
 # re-fetching that small set of git deps. The valuable Berry cache
 # (server-ce-yarn-cache) stays persistent. YARN_NETWORK_CONCURRENCY=1 is kept
 # as cheap insurance against concurrent writes to the fresh cache.
+#
+# Preparing those git deps also makes Yarn Classic fetch esbuild's ~10
+# per-platform binaries, whose downloads occasionally arrive truncated ("the
+# file appears to be corrupt" / missing .yarn-tarball.tgz). Since the tmpfs is
+# fresh each build there is nothing to fall back to, so we wrap the step in a
+# small retry loop that wipes the classic cache and re-fetches before failing.
 RUN --mount=type=cache,target=/root/.cache \
     --mount=type=cache,target=/root/.yarn/berry/cache,id=server-ce-yarn-cache \
     --mount=type=tmpfs,target=/usr/local/share/.cache/yarn \
-    --mount=type=tmpfs,target=/tmp node genScript install | YARN_NETWORK_CONCURRENCY=1 bash
+    --mount=type=tmpfs,target=/tmp \
+    for i in 1 2 3; do \
+      node genScript install | YARN_NETWORK_CONCURRENCY=1 bash && exit 0; \
+      echo "==== install attempt $i failed; wiping Yarn Classic cache and retrying ===="; \
+      rm -rf /usr/local/share/.cache/yarn/* 2>/dev/null || true; \
+    done; \
+    exit 1
 
 # Add the actual source files
 # ---------------------------
@@ -47,8 +59,15 @@ RUN --mount=type=cache,target=/root/.cache \
     --mount=type=tmpfs,target=/usr/local/share/.cache/yarn \
     --mount=type=cache,target=/overleaf/services/web/node_modules/.cache,id=server-ce-webpack-cache \
     --mount=type=tmpfs,target=/tmp \
-    node genScript compile | YARN_NETWORK_CONCURRENCY=1 bash || \
-    (echo "==== PACK LOGS ====" && find /tmp -name pack.log -exec cat {} \; && exit 1)
+    for i in 1 2 3; do \
+      node genScript compile | YARN_NETWORK_CONCURRENCY=1 bash && exit 0; \
+      echo "==== compile attempt $i failed; wiping Yarn Classic cache and retrying ===="; \
+      find /tmp -name pack.log -exec cat {} \; 2>/dev/null || true; \
+      rm -rf /usr/local/share/.cache/yarn/* 2>/dev/null || true; \
+    done; \
+    echo "==== PACK LOGS (all attempts failed) ===="; \
+    find /tmp -name pack.log -exec cat {} \; 2>/dev/null || true; \
+    exit 1
 # Copy runit service startup scripts to its location
 # --------------------------------------------------
 ADD server-ce/runit /etc/service