fix(launcher): detach stdin on agent container run (#5)

pi print mode reads piped stdin until EOF; an attached terminal stdin
blocked the one-shot run forever. Automated contexts (closed stdin)
never exposed it. Request text comes from the compose command.

Proven: tail -f /dev/null | scripts/hello.sh now returns MOSAIC_HELLO_OK
in ~4s (previously timed out at 30s); verify.sh remains green.

Closes #5

scripts/hello.sh

@@ -15,5 +15,8 @@ load_config
 bootstrap_runtime_dir
 
 # -T: no pseudo-TTY, so stdout is clean model output.
+# </dev/null: detach stdin. Pi's print mode reads piped stdin until EOF;
+# an interactive terminal would otherwise block it forever. The request
+# text comes from the compose command, not stdin, so nothing is lost.
 # Errors, if any, go to stderr for diagnostics.
-docker compose run --rm -T mosaic-agent
+docker compose run --rm -T mosaic-agent < /dev/null