i2c-hid on a stack of its own; PSOGM powers off after three minutes

The touchpad driver crashed the ASUS TUF A15 at boot. Its thread runs the
firmware's AML -- _DSM, _PS0, _CRS -- through uACPI at -O0, on an 8 KB
kernel stack, and kernel stacks are one array: running off the end lands
in the next thread's stack, and the machine dies a moment later in some
other code. The thread now runs on a 64 KB stack of its own, through
SCFF's call_on_stack().

And a crashed laptop sat with its fans up until somebody held the power
button, since the other processors keep running. On an ordinary boot the
PSOGM now says it will power off, and does, after three minutes: SLP_TYP
from \_S5, read at boot, written straight to PM1 control with no AML, which
could sleep or wait on a lock a dead processor holds. A verbose boot keeps
the screen up for ever.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4

include/dev/acpi.h

@@ -30,4 +30,5 @@ void   acpi_thread_start(void);
 void   acpi_pci_route(void);
 
 int    acpi_poweroff(void);     // S5; returns only on failure
+void   acpi_poweroff_now(void); // S5 from a panic, no AML; returns only on failure
 int    acpi_reboot(void);       // the FADT reset register; ditto