refactor: group scripts into walker/ wikigen/ bundle/

Organize the 16 loose scripts by concern:
  walker/  -- .wbt save tooling (sand, build_wbt, walker_hashes,
              harvest_hashes, recover_key)
  wikigen/ -- MediaWiki page generators (make_*_wiki, render_wiki)
  bundle/  -- Unity/Odin asset extraction (unitybundle, odin_read,
              extract_*, loot_probe, dump_loot_bytes)

The only cross-script imports (build_wbt->walker_hashes,
extract_loot->odin_read) live within the same folder, so each
script's dir on sys.path[0] keeps them resolving with no code
changes. All data paths are absolute, so the moves don't affect
I/O. Named the code dir wikigen/ to avoid colliding with the
generated wiki/ output dir; ignore the regenerable wiki_site/ render.

bundle/unitybundle.py

@@ -0,0 +1,81 @@
+"""Minimal UnityFS bundle extractor (LZ4/LZ4HC + uncompressed blocks)."""
+import struct
+
+def lz4_decompress(src, dst_size):
+    out=bytearray(); i=0; n=len(src)
+    while i<n:
+        tok=src[i]; i+=1
+        lit=tok>>4
+        if lit==15:
+            while True:
+                bb=src[i]; i+=1; lit+=bb
+                if bb!=255: break
+        out+=src[i:i+lit]; i+=lit
+        if i>=n: break
+        off=src[i]|(src[i+1]<<8); i+=2
+        ml=tok&15
+        if ml==15:
+            while True:
+                bb=src[i]; i+=1; ml+=bb
+                if bb!=255: break
+        ml+=4
+        start=len(out)-off
+        for j in range(ml):
+            out.append(out[start+j])
+    return bytes(out[:dst_size])
+
+def extract(path):
+    """Return (nodes, data_bytes). nodes=[(off,size,flags,name)]."""
+    b=open(path,'rb').read()
+    if b[:7]!=b'UnityFS': raise ValueError('not UnityFS')
+    p=8
+    ver,=struct.unpack_from('>I',b,p); p+=4
+    def rstr(p):
+        e=b.index(b'\x00',p); return b[p:e].decode(), e+1
+    uver,p=rstr(p); ueng,p=rstr(p)
+    size,=struct.unpack_from('>q',b,p); p+=8
+    cblk,=struct.unpack_from('>I',b,p); p+=4
+    ublk,=struct.unpack_from('>I',b,p); p+=4
+    flags,=struct.unpack_from('>I',b,p); p+=4
+    if flags & 0x80:  # blocksInfo at end
+        bi=b[len(b)-cblk:]
+    else:
+        if flags & 0x200:
+            p=(p+15)&~15
+        bi=b[p:p+cblk]; p+=cblk
+    comp=flags&0x3f
+    blocks_info=bi if comp==0 else lz4_decompress(bi,ublk)
+    q=16
+    bc,=struct.unpack_from('>I',blocks_info,q); q+=4
+    blocks=[]
+    for _ in range(bc):
+        u,c,f=struct.unpack_from('>IIH',blocks_info,q); q+=10
+        blocks.append((u,c,f))
+    ncount,=struct.unpack_from('>I',blocks_info,q); q+=4
+    nodes=[]
+    for _ in range(ncount):
+        off,sz,fl=struct.unpack_from('>qqI',blocks_info,q); q+=20
+        e=blocks_info.index(b'\x00',q); name=blocks_info[q:e].decode(); q=e+1
+        nodes.append((off,sz,fl,name))
+    if not (flags & 0x80):
+        pass
+    data=bytearray()
+    for (u,c,f) in blocks:
+        blk=b[p:p+c]; p+=c
+        data += blk if (f&0x3f)==0 else lz4_decompress(blk,u)
+    return nodes, bytes(data)
+
+if __name__=='__main__':
+    import sys,glob
+    needle=sys.argv[1].encode() if len(sys.argv)>1 else b'actualVersion'
+    d='/mnt/d/SteamLibrary/steamapps/common/Sand Playtest/Sand_Data/StreamingAssets/aa/StandaloneWindows64'
+    for f in sorted(glob.glob(d+'/*.bundle')):
+        import os
+        if os.path.getsize(f) > 30_000_000:  # skip huge ones in quick pass
+            continue
+        try:
+            nodes,data=extract(f)
+            if needle in data:
+                print('HIT', os.path.basename(f), 'at', data.find(needle))
+        except Exception as e:
+            print('ERR', os.path.basename(f), e)