feat(a2b): first-pass texture render — full-screen event-CG layer

Wire asset resolution into a live Godot render. VM executes set-texture ->
ResourceMap resolves (scene,resId) -> files[section_base+resId] across all
archives -> pre-converted BMP -> composite behind the dialogue. The full-screen
event-CG layer (EV052*) renders end-to-end from the executed bytecode.

- Age.Engine/Sys4/ResourceMap.cs: Resolve + BMP TexturePath; Paths: asset JSONs
- GodotAdvHost: create/set/draw-texture -> TextureRect in a _stage layer
- IHost.DrawTexture + VM dispatch extended with dst x/y (draw-texture args 7/8)
- project.godot 800x600; convert_agf.py all-archive + --scene batch
- engine 8/8, C# --selftest still byte-matches vm0 trace (VM behaviour unchanged)

Known limitations (next chunk = graphics geometry/blend subsystem):
- sprites + BG* via the CG-load subroutine get garbage dst/size — native ops
  stubbed (0x208 get-texture-size + sprite position/anim chain)
- AE* fades draw opaque/instant (no alpha); no chromakey
- slot model approximates the game's immediate-mode blit-onto-slot-0 canvas
- AGF pre-converted to BMP offline (runtime decoder deferred)
See docs/phase-a-slice-plan.md (A2b section).

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

tools/convert_agf.py

@@ -1,14 +1,26 @@
 #!/usr/bin/env python3
-"""Convert named AGF files (in extracted/DATA2 or DATA5) to BMP via AGF2BMP2AGF.exe,
-into build/textures/. Run: py -3.11 -X utf8 tools/convert_agf.py EV001AA.AGF ..."""
-import os, sys, shutil, subprocess
+"""Convert AGF images to BMP via AGF2BMP2AGF.exe, into build/textures/.
+
+  py -3.11 -X utf8 tools/convert_agf.py EV052CA.AGF BG030A.AGF ...   # named assets
+  py -3.11 -X utf8 tools/convert_agf.py --scene SC0000               # all .AGF in the scene's
+                                                                     # SYS4INI section manifest
+
+Searches every extracted/DATA* dir (DATA1 holds BG/CS/CB/CA/AE/EM sprites, DATA2 the EV CGs).
+"""
+import json
+import os
+import shutil
+import subprocess
+import sys
+
 sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
 import paths
 
-EXE = paths.EXTRACTED / "DATA1" / "AGF2BMP2AGF.exe"  # tool lives in extracted/DATA1
-SRC_DIRS = [paths.EXTRACTED / "DATA2", paths.EXTRACTED / "DATA5"]
+EXE = paths.EXTRACTED / "DATA1" / "AGF2BMP2AGF.exe"     # tool lives in extracted/DATA1
+SRC_DIRS = [paths.EXTRACTED / d for d in ("DATA1", "DATA2", "DATA3", "DATA4", "DATA5")]
 OUT = paths.BUILD / "textures"
 
+
 def find(name):
     for d in SRC_DIRS:
         p = d / name
@@ -16,18 +28,44 @@ def find(name):
             return p
     return None
 
+
+def scene_agfs(scene):
+    """The .AGF asset names in a scene's SYS4INI section manifest."""
+    secs = json.loads((paths.BUILD / "asset-sections.json").read_text(encoding="utf-8"))
+    files = json.loads((paths.BUILD / "asset-index.json").read_text(encoding="utf-8"))["files"]
+    base = secs["scene_base"][scene.upper().removesuffix(".BIN")]
+    end = next(s["end"] for s in secs["sections"] if s["start"] == base)
+    return [files[p]["name"] for p in range(base, end + 1)
+            if files[p]["name"].upper().endswith(".AGF")]
+
+
+def convert(name):
+    src = find(name)
+    if not src:
+        print(f"NOT FOUND: {name}"); return False
+    out_bmp = OUT / (os.path.splitext(name)[0] + ".BMP")
+    if out_bmp.exists():
+        return True
+    tmp = OUT / name
+    shutil.copy(src, tmp)
+    r = subprocess.run([str(EXE), name], cwd=str(OUT), capture_output=True, text=True)
+    tmp.unlink(missing_ok=True)
+    if not out_bmp.exists():
+        print(f"FAILED: {name} ({r.stdout.strip()[:60]})"); return False
+    return True
+
+
 def main(argv):
     OUT.mkdir(parents=True, exist_ok=True)
-    for name in argv:
-        src = find(name)
-        if not src:
-            print(f"NOT FOUND: {name}"); continue
-        tmp = OUT / name
-        shutil.copy(src, tmp)
-        subprocess.run([str(EXE), name], cwd=str(OUT), check=True)
-        tmp.unlink(missing_ok=True)  # drop the copied .AGF, keep the .BMP
-        print(f"converted {name} -> {OUT / (os.path.splitext(name)[0] + '.BMP')}")
+    if argv and argv[0] == "--scene":
+        names = scene_agfs(argv[1])
+        print(f"{argv[1]}: {len(names)} .AGF assets in manifest")
+    else:
+        names = argv
+    ok = sum(convert(n) for n in names)
+    print(f"converted {ok}/{len(names)} -> {OUT.relative_to(paths.REPO)}")
     return 0
 
+
 if __name__ == "__main__":
     sys.exit(main(sys.argv[1:]))