fix: resolve four frontend/backend issues

- Fix ProjectsPage tests by wrapping renders in MemoryRouter (9 passing)
- Improve session auto-naming to 'project / repo / tool' format
- Add missing /users/me/sessions endpoint for sidebar session loading
- Handle git history 500s: catch RuntimeError in endpoints, graceful empty repo handling
- Add git status badge and discard-changes button to FileEditor toolbar

Quality gates: tsc pass, build pass, Python syntax pass

apps/web/src/components/features/git/FileEditor.tsx

@@ -9,14 +9,23 @@ import { Icon } from "../../ui/Icon";
 import { SyntaxHighlighter } from "./SyntaxHighlighter";
 import { detectLanguage } from "../../../utils/language";
 
+interface GitFileStatus {
+  modified: string[];
+  added: string[];
+  deleted: string[];
+  untracked: string[];
+}
+
 interface FileEditorProps {
   projectId: string;
   repoId: string;
+  gitStatus?: GitFileStatus | null;
 }
 
 export const FileEditor: React.FC<FileEditorProps> = ({
   projectId,
   repoId,
+  gitStatus,
 }) => {
   const [searchParams] = useSearchParams();
   const { user } = useAuth();
@@ -31,9 +40,49 @@ export const FileEditor: React.FC<FileEditorProps> = ({
   const [isBinary, setIsBinary] = useState(false);
   const [saving, setSaving] = useState(false);
 
+  const handleDiscard = async () => {
+    if (!filePath) return;
+    try {
+      const response = await apiClient.get(
+        `/projects/${projectId}/repositories/${repoId}/files/content`,
+        {
+          params: {
+            branch,
+            path: filePath,
+          },
+        }
+      );
+      const data = response.data;
+      if (data.is_binary) {
+        setIsBinary(true);
+        setContent("Binary file - cannot display");
+        setOriginalContent("");
+      } else {
+        setIsBinary(false);
+        setContent(data.content);
+        setOriginalContent(data.content);
+      }
+      setMode("view");
+    } catch {
+      setError("Failed to discard changes");
+    }
+  };
+
   const branch = searchParams.get("branch") || "main";
   const filePath = searchParams.get("file");
 
+  const fileStatus = gitStatus
+    ? gitStatus.modified.includes(filePath || "")
+      ? "modified"
+      : gitStatus.added.includes(filePath || "")
+        ? "added"
+        : gitStatus.deleted.includes(filePath || "")
+          ? "deleted"
+          : gitStatus.untracked.includes(filePath || "")
+            ? "untracked"
+            : undefined
+    : undefined;
+
   const loadFile = useCallback(async () => {
     if (!filePath) {
       setContent("");
@@ -158,7 +207,7 @@ export const FileEditor: React.FC<FileEditorProps> = ({
     <div className={styles.fileEditor}>
       <div className={styles.fileEditorToolbar}>
         <div className="file-breadcrumbs">
-          {filePath.split("/").map((part, i, arr) => (
+          {filePath?.split("/").map((part, i, arr) => (
             <span key={i}>
               {part}
               {i < arr.length - 1 && (
@@ -168,6 +217,11 @@ export const FileEditor: React.FC<FileEditorProps> = ({
           ))}
         </div>
         <div className={styles.fileActions}>
+          {fileStatus && (
+            <span className={`git-status-badge ${fileStatus}`} title={fileStatus}>
+              {fileStatus === "modified" ? "M" : fileStatus === "added" ? "A" : fileStatus === "deleted" ? "D" : "?"}
+            </span>
+          )}
           {mode === "view" && !isBinary && (
             <button
               className="btn-primary"
@@ -180,24 +234,33 @@ export const FileEditor: React.FC<FileEditorProps> = ({
           )}
           {mode === "edit" && (
             <>
-          <button
-            className="btn-primary"
-            onClick={handleSave}
-            disabled={content === originalContent || saving}
-            type="button"
-          >
-            {saving ? (
-              <>
-                <Icon name="loading" size="sm" />
-                Saving...
-              </>
-            ) : (
-              <>
-                <Icon name="save" size="sm" />
-                Save
-              </>
-            )}
-          </button>
+              <button
+                className="btn-primary"
+                onClick={handleSave}
+                disabled={content === originalContent || saving}
+                type="button"
+              >
+                {saving ? (
+                  <>
+                    <Icon name="loading" size="sm" />
+                    Saving...
+                  </>
+                ) : (
+                  <>
+                    <Icon name="save" size="sm" />
+                    Save
+                  </>
+                )}
+              </button>
+              <button
+                className="btn-secondary"
+                onClick={handleDiscard}
+                type="button"
+                title="Revert to last committed version"
+              >
+                <Icon name="undo" size="sm" />
+                Discard
+              </button>
               <button
                 className="btn-secondary"
                 onClick={handleCancel}