[ci] remote-security: eis-lifetime fixture misses its 2 s disconnect deadline intermittently #1064

The remote-security job's first check, tests/remote-desktop-reference/eis-lifetime.c (run from tests/remote-desktop-reference/run.sh:18, before any Tuna compositor starts), failed three times on #1057 (run 42903424429, attempts 1–3) and once each on the docs-only #1052 and on anim/compositor-window-motion in the last 30 CI runs; it passed on retry elsewhere and on #1061, which contains #1057's change.

Every failure is the same:

EIS lifetime delivery/disconnect deadline expired: sent=1 acknowledged=1 keys=2 buttons=2 absolute=1 frames=5

All input arrives; after the fixture writes the acknowledgement it waits deadline = eis_now(eis) + 2000000 (2 s, eis-lifetime.c ~line 129) for EIS_EVENT_CLIENT_DISCONNECT from scripts/lib/tuna-remote-ei.c, and that does not arrive in time. The fixture involves only libei/libeis 1.6.0 and the test client, so the failure is independent of compositor changes.

Not yet known: whether the client is slow to exit under runner load (2 s is tight inside a freshly built container) or whether a disconnect is sometimes lost. Retained evidence: artifact remote-security 13812949694 (eis-lifetime.log).

Part of #577 lane CI triage (2026-11-10).