fix(hooks): add null guard for tool.execute.after output (#1054)

/review command and some Claude Code built-in commands trigger
tool.execute.after hooks with undefined output, causing crashes
when accessing output.metadata or output.output.

Fixes #1035

Co-authored-by: sisyphus-dev-ai <sisyphus-dev-ai@users.noreply.github.com>

src/hooks/atlas/index.ts

@@ -663,6 +663,11 @@ export function createAtlasHook(
       input: ToolExecuteAfterInput,
       output: ToolExecuteAfterOutput
     ): Promise<void> => {
+      // Guard against undefined output (e.g., from /review command - see issue #1035)
+      if (!output) {
+        return
+      }
+
       if (!isCallerOrchestrator(input.sessionID)) {
         return
       }