test-ux: session shows "Last login: <stale date>" banner after restart/reuse

[voidfreud]

Observed during integration test run. Some sessions start with a "Last login: Sun Apr 12 22:22:39 on ttys016" banner from days ago; others don't. Appears on sessions that went through async_restart or --reuse, because the shell process retained state from macOS's Terminal greeting mechanism.

Mostly cosmetic — it's confusing in logs and screenshots, and makes it harder to tell which sessions are fresh. Not a bug per se.

Fix options: suppress via ~/.hushlogin in the test harness, or document as "macOS Terminal greeting behavior, not ita."

Priority: low — cosmetic only.

[voidfreud]

Fixed in PR #392 (test-UX bundle). Path.home() / '.hushlogin' touched at conftest import (try/except on failure). Suppresses macOS Terminal 'Last login' banner.