feat: Windows-Kompatibilität

- WorkspaceHelper: Zentrale Hilfsmethoden (IsWindows, TempDir, IsSubPathOf,
  GetRelativePath, ShellExecutable, ShellArguments)
- ToolService: execute nutzt cmd.exe auf Windows, GetRelativePath mit
  Forward-Slashes, IsSubPathOf für case-insensitive Pfadprüfung
- SessionEndpoint: /tmp → Path.GetTempPath(), bash → cmd.exe,
  Fire-and-forget via .bat statt systemd-run auf Windows
- ChatService: /tmp → WorkspaceHelper.TempDir
- MemoryService: IsSubPathOf + GetRelativePath
- WorkspaceEndpoint: HandleBrowse zeigt Laufwerke auf Windows,
  IsSubPathOf statt StartsWith
- InfoEndpoint: gott.exe auf Windows, isWindows-Flag in API-Response
- Frontend: File-Explorer mit Laufwerks-Navigation auf Windows

wwwroot/js/file-explorer.js

@@ -535,7 +535,7 @@ function openFolderBrowser(opts = {}) {
   _feState._keyHandler = (e) => { if (e.key === 'Escape') closeFileExplorer(); };
   document.addEventListener('keydown', _feState._keyHandler);
 
-  fbLoadDir(opts.startPath || '/');
+  fbLoadDir(opts.startPath || (serverIsWindows ? '' : '/'));
 }
 
 async function fbLoadDir(absPath) {
@@ -581,7 +581,7 @@ async function fbLoadDir(absPath) {
 
     const currentNorm = data.current.replace(/\/+$/, '');
     const atBase = _feState.basePath && currentNorm === _feState.basePath;
-    const atRoot = currentNorm === '' || currentNorm === '/';
+    const atRoot = currentNorm === '' || currentNorm === '/' || (serverIsWindows && /^[A-Z]:$/i.test(currentNorm));
     document.getElementById('feBack').disabled = atBase || (atRoot && _feState.history.length === 0);
   } catch (e) {
     sidebar.innerHTML = '<div class="fe-error">Netzwerk-Fehler</div>';
@@ -605,7 +605,14 @@ function fbGoBack() {
     fbLoadDir(prev);
   } else {
     // Kein History-Eintrag → zum Parent navigieren
-    const parent = currentNorm.includes('/') ? currentNorm.substring(0, currentNorm.lastIndexOf('/')) || '/' : '/';
+    let parent;
+    if (serverIsWindows && /^[A-Z]:$/i.test(currentNorm)) {
+      parent = ''; // Laufwerk → zurück zur Laufwerksauswahl
+    } else if (serverIsWindows && /^[A-Z]:\/[^/]*$/i.test(currentNorm)) {
+      parent = currentNorm.substring(0, 2); // z.B. C:/Users → C:
+    } else {
+      parent = currentNorm.includes('/') ? currentNorm.substring(0, currentNorm.lastIndexOf('/')) || (serverIsWindows ? '' : '/') : (serverIsWindows ? '' : '/');
+    }
     if (parent !== currentNorm) {
       fbLoadDir(parent);
     }

wwwroot/js/title.js

@@ -1,7 +1,9 @@
 let buildTime = 0;
+let serverIsWindows = false;
 
 fetch('/api/info').then(r => r.json()).then(data => {
   buildTime = data.buildTime || 0;
+  serverIsWindows = !!data.isWindows;
   updateTitle();
   setInterval(updateTitle, 1000);
 });