fix: harden Docker environment so tests pass inside container

- Add procps to runtime stage so `ps` is available for process management
- Remove noexec from /tmp and /home/storkit tmpfs mounts so test scripts
  can be executed from tempdir
- Update coder agent system_prompt to run clippy --all-targets --all-features
  matching what the server acceptance gate actually runs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker/Dockerfile

@@ -67,6 +67,8 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
         build-essential \
         pkg-config \
         libssl-dev \
+        # procps provides ps, needed by tests and process management
+        procps \
     && rm -rf /var/lib/apt/lists/*
 
 # Node.js in runtime