fix(examples): restore the tui-demo pre-boot TTY refusal and stabilize the PTY smoke

The built-bin fail-loud test needs the TTY refusal before Loader boot (a
compose-time throw is logged per-entry, not rethrown); the PTY driver drops
COLORTERM so a developer's truecolor shell cannot flip the banner to the
gradient path mid-assertion; the scripted fixture persists raw JSONL so the
smoke's system-prompt inspection can read the log.

examples/tui-agent/tests/tui-keyless-smoke.e2e.ts

@@ -22,6 +22,10 @@ env.update({
     "COLUMNS": "100",
     "LINES": "30",
 })
+# Deterministic banner: a developer shell's COLORTERM=truecolor would switch the
+# banner to the per-letter gradient (one SGR per letter), breaking the literal
+# DEEPSEEK assertions. The gradient path has its own unit and snapshot coverage.
+env.pop("COLORTERM", None)
 if resume_session_id:
     env["RESUME_SESSION_ID"] = resume_session_id
 pid, fd = pty.fork()