fix(core): restore the shell no-output placeholder (#51187)

packages/core/src/shell.ts

@@ -240,10 +240,8 @@ const layer = () =>
           if (page.output.endsWith("\n")) lines.pop()
           const truncated = latest.size > maxBytes || lines.length > maxLines
           const text = lines.length > maxLines ? lines.slice(-maxLines).join("\n") : page.output
-          const notice = truncated
-            ? `${text ? "\n\n" : ""}[full output saved to ${info.file}]`
-            : ""
-          return { output: `${text}${notice}`, truncated }
+          const notice = truncated ? `\n\n[full output saved to ${info.file}]` : ""
+          return { output: `${text || "(no output)"}${notice}`, truncated }
         }).pipe(Effect.catchTag("Shell.NotFoundError", () => Effect.succeed(undefined)))
         return { info, capture }
       })

packages/core/test/tool-shell.test.ts

@@ -1555,7 +1555,7 @@ describe("ShellTool", () => {
               {
                 id: settled.metadata?.shellID,
                 status: "completed",
-                output: "Exited with code 7",
+                output: "(no output)\n\nExited with code 7",
               },
             ])
           }),