fix(loader): chown /app/jars to loader so volume init gives wget write perms

Root cause of "Loader exited 1" with `wget: can't open '/app/jars/app.jar':
Permission denied`. DockerRuntimeOrchestrator creates a fresh named volume
per replica and mounts it RW at /app/jars. Docker initializes empty named
volumes from the image's mountpoint contents — but /app/jars didn't exist
in the loader image, so the volume came up as root:root 0755. Loader runs
as UID 1000 and can't write to a root-owned dir.

Pre-create /app/jars in the image owned by `loader`. Volume init now
inherits loader:loader ownership and wget writes app.jar successfully.
Verified locally with the full hardening contract (cap_drop ALL, readonly
rootfs, /tmp tmpfs, no-new-privileges, apparmor=docker-default).

This is the conditional CI build's first real exercise — the loader-build
step gated on cameleer-runtime-loader/** changes will fire on this push
and produce the fixed `:latest` tag.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cameleer-runtime-loader/Dockerfile

@@ -4,7 +4,10 @@ FROM busybox:1.37-musl
 
 # Run as non-root (UID 1000 inside the container; with userns_mode this is
 # remapped to host UID ~101000 — fully unprivileged on the host).
-RUN adduser -D -u 1000 loader
+# Pre-create /app/jars owned by `loader` so the orchestrator's named-volume
+# mount inherits that ownership at first init — without it the empty named
+# volume comes up as root:root 0755 and wget can't write app.jar.
+RUN adduser -D -u 1000 loader && mkdir -p /app/jars && chown -R loader:loader /app
 
 COPY entrypoint.sh /usr/local/bin/loader
 RUN chmod +x /usr/local/bin/loader