feat(root01): author Computing & Linux Foundations, and the real 01->05 prerequisite chain

Adds all 6 ROOT 01 modules (how computers run software, the shell, filesystem navigation,
files & text, processes, users & permissions foundations), each with a real lesson,
demonstration/guided exercise, knowledge check where warranted, a hands-on Lab, and a
reflection — 35 activities, 29 new content files.

Adds 6 new hands-on Linux scenarios (linux-inspect-hardware, linux-shell-basics,
linux-filesystem-navigation, linux-files-and-text, linux-process-management,
linux-permissions-foundations) plus 2 MCQ scenarios, using the existing generic scenario/
validation engine (docs/ROOT_FOUNDATIONS_LAB_STRATEGY.md §1) — every one tested end-to-end via
the real scenario setup/validate API, including negative tests confirming they correctly FAIL
when not actually solved (e.g. the process-management scenario fails while the target process
is still running; the permissions scenario is tested against a real `su - labuser` denial).

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

Adds a real, server-side ROOT 01->02->03->04->05 course prerequisite chain
(courses.prerequisites) — verified live on two students: one who completed ROOT 01 sees ROOT 02
unlock; a fresh student sees ROOT 02 correctly locked while 03/04/05 stay vacuously satisfied
(their own prerequisite courses are still empty). ROOT 06+ and the Capstone are unaffected.

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

scenarios/data/linux-shell-basics.json

@@ -0,0 +1,30 @@
+{
+  "id": "linux-shell-basics",
+  "title": "Reading Exit Codes Like an Engineer",
+  "category": "Linux Fundamentals",
+  "isolation_type": "shared_namespace",
+  "difficulty": "Easy",
+  "type": "task",
+  "weight": 3,
+  "description": "## Reading Exit Codes Like an Engineer\n\nEvery command you run returns an exit code — `0` means success, anything else means failure. Scripts, CI pipelines, and Kubernetes probes all rely on this exact convention.\n\n**Your task:**\n\n1. Run a command that succeeds (e.g. `true`, or `ls` on a directory that exists) and save its exit code to `/srv/shell-lab/success-exit-code.txt`\n2. Run a command that fails (e.g. `ls` on a path that does NOT exist) and save its exit code to `/srv/shell-lab/fail-exit-code.txt`\n3. Look up the manual page for `ls` (`man ls`) and find one option you didn't know about",
+  "hints": [
+    {
+      "title": "Capturing an exit code",
+      "body": "The special variable `$?` holds the exit code of the LAST command that ran — capture it immediately, before running anything else.",
+      "command": "mkdir -p /srv/shell-lab\ntrue\necho $? > /srv/shell-lab/success-exit-code.txt\nls /this-path-does-not-exist 2>/dev/null\necho $? > /srv/shell-lab/fail-exit-code.txt"
+    }
+  ],
+  "setup_commands": [
+    { "command": "mkdir -p /srv/shell-lab" }
+  ],
+  "validation": {
+    "commands": [
+      { "description": "success-exit-code.txt records 0", "command": "cat /srv/shell-lab/success-exit-code.txt", "expected_output": "0", "match": "exact" },
+      { "description": "fail-exit-code.txt records a non-zero code", "command": "cat /srv/shell-lab/fail-exit-code.txt", "expected_output": "^[1-9][0-9]*$", "match": "regex" }
+    ]
+  },
+  "default_namespace": "default",
+  "teardown_commands": [
+    { "command": "rm -rf /srv/shell-lab" }
+  ]
+}