Add comprehensive test suites for answer key validation, API functionality, and code linting

- Introduced `test_answer_key.py` to validate the correctness of answer keys against expected responses, ensuring both false and true answers are graded appropriately.
- Created `test_answer_values.py` to verify the accuracy of answer keys by recomputing values and comparing them against the provided `answers.json`.
- Implemented `test_api.py` to test the HTTP API for suite management, ensuring read-only enforcement and proper handling of custom suites.
- Added `test_code_lint.py` to perform static code analysis, ensuring that all linting rules are enforced without false positives on correct answers.
- Developed `test_collision.py` to guard against prompt mismatches due to filename collisions across suites.
- Created `test_gguf.py` to validate GGUF header parsing and model classification, including handling of malformed input.
- Introduced `test_linter.py` to ensure report rendering preserves content integrity and correctly fences code.
- Added `test_reporting.py` to verify report naming conventions and the accuracy of per-suite score breakdowns.

tests_py/run_all.py

@@ -0,0 +1,71 @@
+"""Run every Python test and summarise. No third-party dependencies.
+
+    python tests_py/run_all.py           # everything
+    python tests_py/run_all.py gguf      # only files matching "gguf"
+
+Each test is a standalone script run in its own process, so one crashing
+cannot take the rest with it, and each starts from a clean import state —
+several load plugins directly, which would otherwise collide in sys.modules.
+
+Exits non-zero if any test fails, so this works as a CI entry point.
+"""
+
+from __future__ import annotations
+
+import subprocess
+import sys
+from pathlib import Path
+
+HERE = Path(__file__).resolve().parent
+
+
+def main() -> int:
+    wanted = sys.argv[1:]
+    tests = sorted(p for p in HERE.glob("test_*.py"))
+    if wanted:
+        tests = [p for p in tests if any(w in p.stem for w in wanted)]
+    if not tests:
+        print("no matching tests")
+        return 1
+
+    results: list[tuple[str, int, str]] = []
+    for path in tests:
+        proc = subprocess.run(
+            [sys.executable, str(path)],
+            capture_output=True,
+            text=True,
+            encoding="utf-8",
+            errors="replace",
+            cwd=str(HERE),
+        )
+        output = (proc.stdout or "") + (proc.stderr or "")
+        print(output.rstrip())
+
+        # The last "N/M passed" line, or a SKIP notice, is the verdict.
+        summary = next(
+            (line.strip() for line in reversed(output.splitlines())
+             if "passed" in line or line.strip().startswith("SKIP")),
+            "no summary",
+        )
+        results.append((path.stem, proc.returncode, summary))
+
+    print("\n" + "=" * 60)
+    print("SUMMARY")
+    print("=" * 60)
+    failed = 0
+    for name, code, summary in results:
+        if "SKIP" in summary:
+            status = "SKIP"
+        elif code == 0:
+            status = "ok"
+        else:
+            status = "FAIL"
+            failed += 1
+        print(f"  {status:<5} {name:<22} {summary}")
+
+    print(f"\n{len(results) - failed}/{len(results)} files ok")
+    return 1 if failed else 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())