chore: initialize age-reimpl repo

Reverse-engineering + open reimplementation workspace for Eushully's AGE/SYS4
engine (first target: Himegari). The repo root is age-reimpl/; the original game
install and the extracted ALF data are siblings outside the repo and are never
tracked. build/ (derived corpora) is gitignored and regenerated by the tools.

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

tools/validate_opcode_table_naive.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+"""Validate Kelebek1's AGE opcode table against Himegari SYS4 scripts.
+
+Model (from Kelebek1 disassembler.cpp + age-shared.cpp):
+  code stream = sequence of instructions.
+  each instruction = <opcode:u32> then argument_count * <arg>, where each arg = <type:u32><value:u32>.
+  => instruction length in dwords = 1 + 2*argument_count  (uniform; type-2/0x64 args seek elsewhere, don't consume inline)
+  arg type 2 = inline string (value = dword offset into body). types: 0 imm,1 float,3 g-int,9 l-int, etc.
+A clean decode consumes exactly code_len dwords with no unknown opcode and no arg overrun.
+"""
+import os, re, sys, collections
+from pathlib import Path
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+import paths
+import sys4load
+
+CPP = paths.KELEBEK_CPP.read_text(encoding="utf-8")
+# parse {0x1F4, "label", 0x0},
+TABLE = {}
+LABEL = {}
+for m in re.finditer(r'\{\s*(0x[0-9A-Fa-f]+)\s*,\s*"([^"]*)"\s*,\s*(0x[0-9A-Fa-f]+)\s*\}', CPP):
+    op = int(m.group(1), 16); lbl = m.group(2); argc = int(m.group(3), 16)
+    TABLE[op] = argc; LABEL[op] = lbl
+print(f"parsed {len(TABLE)} opcode defs from Kelebek1 table (max op 0x{max(TABLE):x})")
+
+files = paths.scripts()
+
+clean = dirty = parsefail = 0
+unknown_ops = collections.Counter()
+fail_examples = []
+str_ok = str_bad = 0
+opcode_use = collections.Counter()
+
+for name, p in sorted(files.items()):
+    try:
+        scr = sys4load.load(p)
+    except Exception:
+        parsefail += 1; continue
+    dw = scr.dwords; cl = scr.code_len
+    i = 0; ok = True; reason = ""
+    while i < cl:
+        op = dw[i]
+        if op not in TABLE:
+            unknown_ops[op] += 1; ok = False; reason = f"unknown op 0x{op:x} @{i}"; break
+        opcode_use[op] += 1
+        argc = TABLE[op]
+        # check each arg's type; resolve strings
+        base = i + 1
+        if base + 2*argc > cl:
+            ok = False; reason = f"arg overrun op 0x{op:x} @{i} needs {argc} args"; break
+        for a in range(argc):
+            atype = dw[base + 2*a]; aval = dw[base + 2*a + 1]
+            if atype == 2:  # inline string
+                if 0 <= aval < scr.nbody:
+                    txt, nd = sys4load._decode_string(dw, aval)
+                    if txt is None: str_bad += 1
+                    else: str_ok += 1
+                else:
+                    str_bad += 1
+        i = base + 2*argc
+    if ok and i == cl:
+        clean += 1
+    else:
+        dirty += 1
+        if len(fail_examples) < 15:
+            fail_examples.append(f"  {name}: {reason} (stopped @{i}/{cl})")
+
+print(f"\n== decode result over {len(files)} scripts ==")
+print(f"  clean (fully consumed, all opcodes known): {clean}")
+print(f"  dirty: {dirty}")
+print(f"  parse-fail (container): {parsefail}")
+print(f"  string args resolved ok / bad: {str_ok} / {str_bad}")
+print(f"\ntop unknown opcodes (op: files affected):")
+for op, c in unknown_ops.most_common(25):
+    print(f"  0x{op:x}: {c}")
+print(f"\nsample dirty files:")
+print("\n".join(fail_examples))
+print(f"\ntop 25 opcodes actually used in Himegari (op label count):")
+for op, c in opcode_use.most_common(25):
+    print(f"  0x{op:<4x} {LABEL.get(op,'?'):22} {c}")