feat(cli): log shell command output to a file

This change modifies the `shellCommandProcessor` to write the complete
output of any executed shell command to a log file in the /tmp
directory.

The filename is formatted as `gemini-cli-output-<timestamp>.log`.

This provides a persistent record of shell command interactions for
debugging and auditing purposes, without altering the user-facing
display in the CLI.

packages/cli/src/ui/hooks/shellCommandProcessor.ts

@@ -231,6 +231,13 @@ export const useShellCommandProcessor = (
                 }
               }
 
+              const outputFilePath = path.join(os.tmpdir(), `gemini-cli-output-${userMessageTimestamp}.log`);
+              fs.writeFile(outputFilePath, finalOutput, (err) => {
+                if (err) {
+                  onDebugMessage(`Failed to write shell output to ${outputFilePath}: ${err.message}`);
+                }
+              });
+
               const finalToolDisplay: IndividualToolCallDisplay = {
                 ...initialToolDisplay,
                 status: finalStatus,