Add beginner-safe solution support and local learning tracks

.github/linters/actionlint.yaml

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+---
+# Super-Linter loads ActionLint rules from this directory.
+# Its bundled label catalog predates GitHub-hosted ubuntu-24.04.
+self-hosted-runner:
+  labels:
+    - ubuntu-24.04

.github/scripts/p2_classroom_check.py

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+#!/usr/bin/env python3
+"""Validate the minimum classroom evidence contract for all active projects."""
+
+from __future__ import annotations
+
+import json
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[2]
+MANIFEST = ROOT / "config" / "active-integrity-manifest.json"
+REQUIRED = ("P2_CLASSROOM.md", "P2_EVIDENCE.md", "P2_LOCAL_PILOT.md", "START_HERE.md")
+
+
+def main() -> int:
+    projects = json.loads(MANIFEST.read_text(encoding="utf-8"))["projects"]
+    failures: list[str] = []
+    for entry in projects:
+        root = ROOT / entry["project"]
+        for name in REQUIRED:
+            if not (root / name).is_file():
+                failures.append(f"{entry['project']}/{name}")
+        classroom = root / "P2_CLASSROOM.md"
+        if (
+            classroom.is_file()
+            and "## Learning and assessment"
+            not in classroom.read_text(encoding="utf-8")
+        ):
+            failures.append(
+                f"{entry['project']}/P2_CLASSROOM.md missing Learning and assessment"
+            )
+    if failures:
+        print(
+            "ERROR: classroom contract failures: " + ", ".join(failures),
+            file=sys.stderr,
+        )
+        return 1
+    print(f"P2 classroom contract: PASS ({len(projects)} projects)")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

INSTRUCTOR_SOLUTION_PACK.md

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+# Instructor Solution Pack Boundary
+
+> Complete worked solutions are intentionally stored in the separately distributed instructor pack, not in this student-facing repository.
+
+Every active project now includes `START_HERE.md`, which provides a local-safe starting action, observable
+checkpoints, non-spoiling hints, and expected evidence. Instructors should retain the separate solution pack
+and release assistance progressively.