Use the single-handle *-shm locking scheme on Windows network volumes.

SQLite 3.50 split WAL shared-memory locking across two file handles, which
does not work on network filesystems; 3.51.0 added bUseSharedLockHandle to
restore the single-handle scheme, but selects it with winIsUNCPath(), which
cannot recognize a drive letter mapped to an SMB share. This asks the OS
instead. See bug 2067771.

Upstream check-in: https://sqlite.org/src/info/52ed3b490a4d03ef
  "On Windows, use the GetDriveTypeW() interface to detect network
   filesystems and always use a single shared file handle for the -shm
   files on such filesystems."  (drh, 2026-09-03)
  Git mirror: sqlite/sqlite@28fe5623286bdb4eaf543e7be4dddee5762ee51b

Ported to the amalgamation: upstream's aSyscall[] has 59 entries
(cygwin_conv_path at 58), ours has 81 (at 80), so GetDriveTypeW is index 81
here and the ArraySize() assertion moves 81 -> 82.

Deviates from upstream in one place: the osGetDriveTypeW cast keeps WINAPI.
GetDriveTypeW is __stdcall, so calling it through a __cdecl pointer drifts
ESP by 4 bytes per call on win32 builds.

Remove this file once we vendor a SQLite release containing the upstream
check-in.

diff --git a/sqlite3.c b/sqlite3.c
index 0644a39f8734..f474acb2c2ff 100644
--- a/sqlite3.c
+++ b/sqlite3.c
@@ -49927,6 +49927,9 @@ static struct win_syscall {
 #define osCygwin_conv_path ((size_t(*)(unsigned int, \
     const void *, void *, size_t))aSyscall[80].pCurrent)
 
+  { "GetDriveTypeW",            (SYSCALL)GetDriveTypeW,          0 },
+#define osGetDriveTypeW ((UINT(WINAPI*)(LPCWSTR))aSyscall[81].pCurrent)
+
 }; /* End of the overrideable system calls */
 
 /*
@@ -53054,6 +53057,23 @@ static int winIsUNCPath(const char *zFile){
   return sqlite3_win_test_unc_locking;
 }
 
+/*
+** Return true if the string passed in is the name of a file on a
+** remote (network-mounted) volume.
+*/
+static int winIsRemoteVolume(const char *zFile){
+  WCHAR zRoot[4];
+  if( strncmp(zFile, "\\\\?\\",4)==0 ) zFile += 4;
+  if( !sqlite3Isalpha(zFile[0]) ) return 0;
+  if( zFile[1]!=':' ) return 0;
+  if( !winIsDirSep(zFile[2]) ) return 0;
+  zRoot[0] = (WCHAR)zFile[0];
+  zRoot[1] = ':';
+  zRoot[2] = '\\';
+  zRoot[3] = 0;
+  return osGetDriveTypeW(zRoot)==DRIVE_REMOTE;
+}
+
 /*
 ** Open the shared-memory area associated with database file pDbFd.
 */
@@ -53079,7 +53099,11 @@ static int winOpenSharedMemory(winFile *pDbFd){
   pNew->zFilename = (char*)&pNew[1];
   pNew->hSharedShm = INVALID_HANDLE_VALUE;
   pNew->isUnlocked = 1;
-  pNew->bUseSharedLockHandle = winIsUNCPath(pDbFd->zPath);
+  if( winIsUNCPath(pDbFd->zPath) || winIsRemoteVolume(pDbFd->zPath) ){
+    pNew->bUseSharedLockHandle = 1;
+  }else{
+    pNew->bUseSharedLockHandle = 0;
+  }
   sqlite3_snprintf(nName+15, pNew->zFilename, "%s-shm", pDbFd->zPath);
   sqlite3FileSuffix3(pDbFd->zPath, pNew->zFilename);
 
@@ -55261,7 +55285,7 @@ SQLITE_API int sqlite3_os_init(void){
 
   /* Double-check that the aSyscall[] array has been constructed
   ** correctly.  See ticket [bb3a86e890c8e96ab] */
-  assert( ArraySize(aSyscall)==81 );
+  assert( ArraySize(aSyscall)==82 );
   assert( strcmp(aSyscall[0].zName,"AreFileApisANSI")==0 );
   assert( strcmp(aSyscall[20].zName,"GetFileAttributesA")==0 );
   assert( strcmp(aSyscall[40].zName,"HeapReAlloc")==0 );