fix(summer): give delegated commands the terminal and keep their stderr apart

- appStreams hands the app binary summer's own stdout and stderr on a
  terminal, so it asks the production question, prints styled summaries
  and animates its widgets
- off a terminal the binary's stdout goes through summer's Output and its
  stderr to summer's stderr, so --json and -q output carry no log lines
- newAppCmd (unexported) takes the two writers; docs say the streams stay
  apart (CR-03)

docs/console/introduction.md

@@ -141,6 +141,8 @@ summer -v migrate --pretend
 summer admin:token:create jane --scope journal.posts --json
 ```
 
+The binary writes to your terminal directly, so it asks the production question, prints its styled startup summary and animates its spinners as if you had run it yourself. Its error stream stays separate from its output: `summer route:list --json > routes.json` captures only the JSON, while warnings and log lines still reach the terminal on stderr.
+
 When the binary fails, `summer` exits with the binary's exit code (a usage error stays `2`) and prints nothing more: the binary has already printed its error. A binary killed by a signal gets an error block from `summer` and exit code `1`.
 
 When `summer` receives SIGINT or SIGTERM while the binary runs, it passes the signal on and waits for the binary to shut down, so stopping `summer serve` with Ctrl+C or `kill` frees its port.