feat: SCJUMP decoder scaffold — CFG acyclic check + chapter dispatch (Task 1)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tools/test_scjump.py

@@ -0,0 +1,22 @@
+#!/usr/bin/env python3
+"""Standalone tests for the SCJUMP decoder. Run: py -3.11 -X utf8 tools/test_scjump.py"""
+import os, sys, json
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+import scjump_decode as S
+
+FAILS = []
+def check(cond, msg):
+    print(("  ok  " if cond else " FAIL ") + msg)
+    if not cond: FAILS.append(msg)
+
+def test_cfg_acyclic_and_dispatch():
+    scr = S.load_scjump()
+    check(S.forward_edges_only(scr), "SCJUMP CFG is acyclic (all code edges forward)")
+    disp = S.chapter_dispatch(scr)
+    expected = {1:0x81, 2:0x9f, 3:0x1ded, 4:0x1e6d, 5:0x54c1, 6:0x93c4, 7:0x1e868, 8:0x2aa42, 9:0x2b8a3}
+    check(disp == expected, f"chapter dispatch matches known offsets (got {disp})")
+
+if __name__ == "__main__":
+    test_cfg_acyclic_and_dispatch()
+    print(f"\n{len(FAILS)} failures")
+    sys.exit(1 if FAILS else 0)