Optimize runner image: remove unused packages, reorder layers

Remove net-tools (legacy, iproute2 suffices), sudo (running as root),
and jq (unused). Reorder layers from stable to volatile for better
Docker cache hit rates.

Author: manascb1344

app.py

@@ -147,24 +147,19 @@ def format(self, record: logging.LogRecord) -> str:
 runner_image = (
     modal.Image.from_registry("ubuntu:22.04")
     .env({"DEBIAN_FRONTEND": "noninteractive"})
+    # Layer 1: System deps + Docker setup (stable, rarely changes)
     .apt_install(
         "wget",
         "ca-certificates",
         "curl",
-        "net-tools",
         "iproute2",
         "git",
-        "sudo",
-        "jq",
     )
     .run_commands(
         "install -m 0755 -d /etc/apt/keyrings",
         "curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc",
         "chmod a+r /etc/apt/keyrings/docker.asc",
-        'echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] '
-        "https://download.docker.com/linux/ubuntu "
-        '$(. /etc/os-release && echo \\"${UBUNTU_CODENAME:-$VERSION_CODENAME}\\") stable" '
-        "| tee /etc/apt/sources.list.d/docker.list > /dev/null",
+        'echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu $(. /etc/os-release && echo \\"${UBUNTU_CODENAME:-$VERSION_CODENAME}\\") stable" | tee /etc/apt/sources.list.d/docker.list > /dev/null',  # noqa: E501
     )
     .apt_install(
         "docker-ce=5:27.5.0-1~ubuntu.22.04~jammy",
@@ -181,15 +176,16 @@ def format(self, record: logging.LogRecord) -> str:
         "update-alternatives --set iptables /usr/sbin/iptables-legacy",
         "update-alternatives --set ip6tables /usr/sbin/ip6tables-legacy",
     )
+    # Layer 2: Python deps (semi-stable)
     .apt_install("python3", "python3-pip", "python-is-python3")
     .pip_install("fastapi==0.115.0", "httpx==0.27.0")
+    # Layer 3: Runner binary (changes with RUNNER_VERSION)
     .run_commands(
         "mkdir -p /actions-runner",
-        f"curl -L https://github.com/actions/runner/releases/download/"
-        f"v{RUNNER_VERSION}/actions-runner-linux-x64-{RUNNER_VERSION}.tar.gz"
-        " | tar -xz -C /actions-runner",
+        f"curl -L https://github.com/actions/runner/releases/download/v{RUNNER_VERSION}/actions-runner-linux-x64-{RUNNER_VERSION}.tar.gz | tar -xz -C /actions-runner",  # noqa: E501
         "/actions-runner/bin/installdependencies.sh",
     )
+    # Layer 4: Local files (most volatile)
     .add_local_file(_TEMP_DOCKERD_PATH, "/start-dockerd.sh", copy=True)
     .run_commands("chmod +x /start-dockerd.sh")
 )