Improve installer diagnostics and rollback reporting

README.md

@@ -26,6 +26,7 @@ WinForms tool for controlled Microsoft BizTalk Server 2020 platform operations d
 - Clear and Close actions in the main toolbar
 - No compile-time dependency on BizTalk ExplorerOM assemblies
 - Transactional Windows installer/updater with SHA-256 payload validation and rollback
+- Installer diagnostics with stable phase codes, complete child-process output, exception chains and a ProgramData-to-Temp log fallback
 - WMI-free runtime self-test plus automated regression test executable
 
 ## Safe Usage
@@ -80,6 +81,8 @@ Snapshot and plan JSON files are written as UTF-8 without BOM. Loading is tolera
 
 JSON snapshots and plans are written through a same-directory temporary file and atomic replacement. Snapshot comparison keys artifacts by application plus name, preventing collisions between equal artifact names in different applications. CSV fields that could be interpreted as spreadsheet formulas are neutralized.
 
+Installer, update and uninstall diagnostics are retained for 90 days under `%ProgramData%\BizTalkPlatformManagementTool\InstallerLogs`. The setup UI can open that directory directly. If the primary log cannot be created, setup reports and uses a `%TEMP%\BizTalkPlatformManagementTool\InstallerLogs` fallback. See [Installation](Installation.md#installer-diagnose) for phase codes and the support checklist.
+
 ## Build
 
 Open `BizTalkPlatformManagementTool.sln` in Visual Studio on Windows with the .NET Framework 4.6.1 Developer Pack installed, then build the `Release|Any CPU` configuration.