scripts: keep PASSED/FAILED color when --timing pipes pytest output

--timing captures pytest's stdout through a Popen pipe so we can
extract the durations section. pytest's --color=auto then sees a
non-TTY on the other end of the pipe and turns ANSI color off, so
green PASSED / red FAILED disappear in the user's terminal.

Pass --color=yes when our own stdout is itself a TTY (so the user
will see the codes rendered) but leave color off when the user is
piping run_tests.py to a file or another process — same heuristic
pytest's auto would have used if it could see past our capture.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: tridge

scripts/run_tests.py

@@ -130,7 +130,13 @@ def build_pytest_cmd(j, extra_args, target_args, timing=False):
     if n is not None:
         cmd += ['-n', str(n)]
     if timing:
+        # We pipe pytest's output to capture it; pytest's --color=auto
+        # then sees a non-TTY and turns colors off. Force them back on if
+        # OUR own stdout is a TTY so the user still sees green PASSED /
+        # red FAILED in interactive runs.
         cmd += ['--durations=0', '--durations-min=0']
+        if sys.stdout.isatty():
+            cmd += ['--color=yes']
     return cmd + extra_args + target_args