feat(root02): author Linux Administration & Networking

Adds all 6 ROOT 02 modules (Linux system administration, storage & filesystems, the
Networking Mental Model, Linux network inspection, DNS & HTTP, Linux troubleshooting) — 37
activities, each with a real lesson, demonstration/guided exercise, knowledge check, hands-on
Lab, and reflection. The Networking Mental Model module (M3) gets deliberately extra depth per
its "critical module" designation, with no lab by design — conceptual mastery via knowledge
check and guided exercise, matching root-05-m00's own precedent.

Adds 6 new hands-on Linux/networking scenarios plus 2 MCQs: linux-service-inspection (inspects
the platform's own real nginx without touching it — a genuinely safe, real service-inspection
target that avoids ever risking the Lab's own connectivity), linux-service-lifecycle (start/
verify/stop a fully controllable service), linux-storage-inspection, linux-network-inspection
(ip/ss/getent/curl, each framed as answering one specific diagnostic question),
linux-dns-http-diagnosis (a genuine DNS-resolves-but-wrong-port failure, diagnosed and fixed),
and linux-troubleshooting-framework (a real missing-config-file failure, resolved via the
RootNode Observe/Evidence/Hypothesis/Test/Repair/Validate/Prevent framework). All tested
end-to-end via the real scenario-validation API, including negative tests confirming they fail
when unsolved.

Wires rootnode-linux-networking-assessment (2 required + 4 random-draw scenarios) using the
existing Phase 3B assessment engine.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

scenarios/data/linux-service-lifecycle.json

@@ -0,0 +1,37 @@
+{
+  "id": "linux-service-lifecycle",
+  "title": "Start, Verify, and Stop a Service",
+  "category": "Linux Administration",
+  "isolation_type": "shared_namespace",
+  "difficulty": "Easy",
+  "type": "task",
+  "weight": 4,
+  "description": "## Start, Verify, and Stop a Service\n\nUnlike the previous exercise (inspecting a service you must never touch), this one is yours to fully control.\n\n**Your task:**\n\n1. Start a small HTTP service in the background, listening on port 8890: `python3 -m http.server 8890 --directory /srv/service-lab &`, and save its PID to `/srv/service-lab/service.pid`\n2. Confirm it's actually listening, and record the result to `/srv/service-lab/status-before.txt` (write exactly `listening`)\n3. Stop it using the PID you saved\n4. Confirm it's actually gone, and record the result to `/srv/service-lab/status-after.txt` (write exactly `stopped`)",
+  "hints": [
+    {
+      "title": "Starting and recording the PID",
+      "body": "`$!` after backgrounding a command holds its PID.",
+      "command": "mkdir -p /srv/service-lab\npython3 -m http.server 8890 --directory /srv/service-lab >/srv/service-lab/service.log 2>&1 &\necho $! > /srv/service-lab/service.pid"
+    },
+    {
+      "title": "Verifying and stopping",
+      "body": "`ss -lnt | grep 8890` confirms it's listening. `kill $(cat .../service.pid)` stops it using the PID you recorded, not a hardcoded number.",
+      "command": "ss -lnt | grep 8890 && echo listening > /srv/service-lab/status-before.txt\nkill $(cat /srv/service-lab/service.pid)\nsleep 1\nss -lnt | grep 8890 || echo stopped > /srv/service-lab/status-after.txt"
+    }
+  ],
+  "setup_commands": [
+    { "command": "mkdir -p /srv/service-lab" }
+  ],
+  "validation": {
+    "commands": [
+      { "description": "confirmed the service was actually listening before stopping it", "command": "cat /srv/service-lab/status-before.txt", "expected_output": "listening", "match": "exact" },
+      { "description": "confirmed the service is actually stopped now", "command": "cat /srv/service-lab/status-after.txt", "expected_output": "stopped", "match": "exact" },
+      { "description": "the process is genuinely no longer running", "command": "kill -0 $(cat /srv/service-lab/service.pid) 2>/dev/null && echo RUNNING || echo GONE", "expected_output": "GONE", "match": "exact" },
+      { "description": "port 8890 is genuinely no longer bound", "command": "ss -lnt | grep -q 8890 && echo BOUND || echo FREE", "expected_output": "FREE", "match": "exact" }
+    ]
+  },
+  "default_namespace": "default",
+  "teardown_commands": [
+    { "command": "[ -f /srv/service-lab/service.pid ] && kill $(cat /srv/service-lab/service.pid) 2>/dev/null; rm -rf /srv/service-lab" }
+  ]
+}