Further improve U01 command-line handoff and temp update path matching

Author: Dutchman101

Client/loader/Main.cpp

@@ -42,8 +42,12 @@ namespace
         ERROR_INSTALL_CONTINUE = -4
     };
 
-    // Command line constants
-    constexpr size_t MAX_CMD_LINE_LENGTH = 4096;
+    // Command line constants. Sized to hold the Windows command-line maximum (CreateProcess limit
+    // is 32767 wchar_t, see CreateProcessW docs). The auto-update flow serializes the sequencer
+    // snapshot through this buffer (CInstallManager::_MaybeSwitchToTempExe -> ShellExecuteNonBlocking
+    // -> Process C lpCmdLine), so a smaller cap silently truncates restored state and breaks the
+    // INSTALL_ROOT carry that prevents U01 in temp-launched processes.
+    constexpr size_t MAX_CMD_LINE_LENGTH = 32768;
 
     // Report log IDs
     constexpr int LOG_ID_END = 1044;

Client/loader/Utils.cpp

@@ -679,7 +679,10 @@ bool IsTemporaryUpdateLaunchPath(const SString& strLaunchPath)
     if (!strLaunchPath.ContainsI("\\upcache\\"))
         return false;
 
-    return ExtractFilename(strLaunchPath).ContainsI("_tmp_");
+    // The auto-update flow creates the extraction directory in Install.cpp::CheckOnRestartCommand
+    // as MakeUniquePath("...\\upcache\\_<archiveName>_tmp_"), so the leaf always begins with '_'.
+    const SString strLeaf = ExtractFilename(strLaunchPath);
+    return strLeaf.BeginsWith("_") && strLeaf.ContainsI("_tmp_");
 }
 
 void SetMTASAPathSource(bool bReadFromRegistry)

Shared/sdk/SharedUtil.Misc.hpp

@@ -405,7 +405,10 @@ static bool IsTemporaryUpdateLaunchPath(const SString& strLaunchPath)
     if (!strLaunchPath.ContainsI("\\upcache\\"))
         return false;
 
-    return ExtractFilename(strLaunchPath).ContainsI("_tmp_");
+    // The auto-update flow creates the extraction directory in Install.cpp::CheckOnRestartCommand
+    // as MakeUniquePath("...\\upcache\\_<archiveName>_tmp_"), so the leaf always begins with '_'.
+    const SString strLeaf = ExtractFilename(strLaunchPath);
+    return strLeaf.BeginsWith("_") && strLeaf.ContainsI("_tmp_");
 }
 
 // Read Last Run Location from a specific registry view. viewFlag should be one of