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>

docs/script-inventory.md

@@ -0,0 +1,110 @@
+# DATA1 Script Inventory — 481 `.BIN` files
+
+All scripts share the magic header `SYS4422 ` (8 bytes), confirming a uniform SYS4
+bytecode format (engine version 4.4.2.2) across the entire set. Header is followed
+by what appear to be little-endian u32 fields (version/section table — to be mapped
+during disassembler work).
+
+Source: `extracted\DATA1\` (extracted from `DATA1.ALF`).
+
+**Patch overrides:** 52 loose `.BIN` files sit in the game root directory and shadow
+their DATA1 counterparts at runtime (sizes differ slightly — e.g. `FIELD.BIN` root
+200,536 vs archive 200,224). These are the v1.03 / append-patch versions and should be
+treated as **authoritative** over the archive copies. Two engine files exist only in
+the root: `SYS4INI.BIN` (272 KB) and `SYS4AB.BIN` (1.08 MB).
+
+---
+
+## Breakdown by series
+
+| Series | Count | Total size | Role (inferred) |
+|---|---|---|---|
+| `SC####` | 136 | 15.6 MB | Scenario/event scripts (numbered 0000–1690, step 10) |
+| `SP####` | 163 | 10.6 MB | Secondary scene series (0010–1369; incl. `SP0051A/B` split) — likely character/H-events |
+| Named scripts | 175 | ~7.5 MB | Engine subsystems, data tables, UI, battle logic |
+| `DEBUG*` | 5 | 1.4 MB | Debug tools (`DEBUGADV.BIN` alone is 1.4 MB — a scene viewer/jump menu) |
+| `RTN_M###` / `RTN_B###` | 26 | ~70 KB | Small routine scripts (map routines M001–M061, battle routines B001–B004) |
+
+### SC series notes
+- Numbered `SC0000`–`SC0880` (main chapters, largest files — up to 700 KB) and
+  `SC1000`–`SC1690` (smaller; likely sub-events, endings, appendix content).
+- `SCJUMP.BIN` (778 KB) is almost certainly the master scene-dispatch/jump table.
+- `SCINIT.BIN` (88 KB) initializes scenario state.
+
+---
+
+## Named scripts by subsystem (inferred from names)
+
+### Engine core / boot flow
+`SYSTEM4.BIN` (config root), `INIT.BIN` (64 bytes — smallest script, ideal first
+disassembly target), `INITCONFIG`, `LOADCONFIG`, `CONFIG`, `TUNE`, `LOGO`, `OP`,
+`ED`, `TITLE`, `GAMESTART`, `GAMECLEAR`, `STAGECLEAR`
+
+### Data-table INIT scripts (likely static game data, not logic)
+Large, table-like scripts — prime candidates for data extraction:
+- `STINIT` (579 KB) — stages/scenario tables
+- `EBINIT` (338 KB) — enemy battle data
+- `MPINIT` (330 KB) — maps
+- `SCINIT` (88 KB), `CGINIT` (79 KB — CG gallery), `ITINIT` (70 KB — items),
+  `RTINIT` (67 KB), `CCINIT` (41 KB), `SKINIT` (37 KB — skills), `CDINIT` (31 KB),
+  `BTANINIT` (105 KB — battle animations)
+- Smaller: `AFINIT`, `ALINIT`, `CIINIT`, `CNINIT`, `CTINIT`, `CVINIT`, `ILINIT`,
+  `LAINIT`, `MAINIT`, `OBINIT`, `SPINIT`, `TRINIT`, `VIINIT`
+
+### Message/string tables (`*MES`)
+`ITMES` (64 KB — item text), `VIMES` (43 KB), `EIMES` (37 KB), `SKMES` (31 KB — skill
+text), `CIMES` (15 KB), `MAMES`, `INFOMES`, `MES` — where most translatable text
+outside scenes lives.
+
+### Battle system
+`BTL` (61 KB — main battle loop), `BTRTN`, `ROUND`, `AIM`, `ATSEEK`, `MVSEEK`,
+`MVRTN`, `MAGIC`, `USEMAGIC`, `SUMMON`, `EXILE`, `DISARM`, `RECOVER`, `COUNTUNIT`,
+`SETOCC`, and the `CALC*` family: `CALCBTPARAM`, `CALCDMG` (16 KB — damage formula!),
+`CALCSCOPE`, `CALCOCC`, `CALCREVISE`, `CALCCC`, `CALCILL`, `CALCARR`
+
+### Dungeon/map engine
+`FIELD` (200 KB — the core dungeon-crawl loop), `DRAWMAP`, `RENDERMAP`,
+`DRAWMINIMAP`, `DRAWCH`/`DRAWCHP`/`DRAWENP`/`DRAWOBJ`/`DRAWTIP`/`DRAWVOL`,
+`SETCH`/`SETEN`/`SETLAND`/`SETOBJ`/`SETROUTE`/`SETMVWORK`,
+`DELCH`/`DELEN`/`DELENMASS`/`DELLAND`, `RESETLAND`, `WARPU`/`WARPD`, `LOOK`,
+`READICON`
+
+### Unit/party management
+`ADDEXP`, `ADDSKILL`, `ADDEN`, `ADDITEM`, `ADDRANDOMITEM`, `LOSTRANDOMITEM`,
+`ADDILL`/`ADDILLSUB`, `EVOLVE`, `IMPROVE` (37 KB), `TRAIN`, `STUDY`, `UNITECH`,
+`REMOVECH`, `SHOWGROW`, `STATUS`, `USEITEM`, `SETCH`
+
+### Base/facility gameplay
+`CAMP`, `ROOM`, `FORT`, `ALCHEMY` (40 KB), `SALLY` (40 KB — sortie/deployment),
+`READY` (39 KB — pre-battle prep), `SELSTAGE` (34 KB), `SELACT` (30 KB)
+
+### Menus / UI / meta
+`MENU`, `CHMENU` (69 KB — character menu), `INFO`/`INFOAF`/`INFOCH`/`INFOEN`/
+`INFOIT`/`INFOVO` (info panels: characters, enemies, items, voices), `SAVE` (40 KB),
+`HISTORY`, `HIDEWIN`, `CLOSE`, `INPUTNAME` (28 KB), `CGMODE` (24 KB — gallery),
+`MMODE` (music mode), `HMODE` (22 KB — scene replay)
+
+### Flow control / branching
+`BUNKI` (分岐 = branch, 15 KB), `SBUNKI`, `BUNKIMOVE`, `SBUNKIMOVE`, `SCJUMP`
+
+### Callbacks (engine → script hooks)
+`CALLBACK_LOAD`, `CALLBACK_LOST`, `CALLBACK_SETTING`, `CALLBACK_WINDOW`
+
+### Debug
+`DEBUG`, `DEBUGADV` (1.4 MB), `DEBUGANIME`, `DEBUGBTL`, `DEBUGMAP` (+2 numbered)
+
+---
+
+## Implications for the port
+
+1. **Much more game logic lives in bytecode than expected.** Damage formulas
+   (`CALCDMG`), the dungeon loop (`FIELD`), battle flow (`BTL`, `ROUND`), and unit
+   progression (`ADDEXP`, `EVOLVE`) are all scripts — `AGE.EXE` is closer to a pure
+   VM/renderer. This strengthens the case for **re-implementing the AGE VM in Godot**
+   rather than transpiling every script by hand (the doc's open question #12).
+2. **Disassembler bootstrapping order** (small → large, system → scene):
+   `INIT.BIN` (64 B) → `ED.BIN`/`OP.BIN`/`LOGO.BIN` (~230 B) → `CALLBACK_LOST`
+   (176 B) → `MENU.BIN` (3 KB) → `CALCDMG` → a mid-size `SC####`.
+3. **The `*INIT` giants are likely data tables**, decodable early even with a
+   partial opcode map — instant win for extracting item/skill/enemy/stage databases.
+4. **Use root-directory overrides, not archive copies**, for the 52 patched scripts.