Start the main thread with COP0 Status.IE set

[Sinan-Karakaya]

Guest code reads COP0 Status to decide whether interrupts are enabled, and two different bits are involved:

bit	name	who sets it
0	IE	the architectural MIPS interrupt enable. The kernel sets it once during boot and normally leaves it set
16	EIE	the EE-specific enable that ei / di toggle

We never execute the boot ROM, so nothing set either one, and R5900Context started with Status at 0.

That is not cosmetic. libkernel's StartThread opens with

mfc0  $v0, Status
xori  $v0, $v0, 1
andi  $v0, $v0, 1     ; -> 1 when IE is clear

and returns -1 when that is true: its "you must call iStartThread from an interrupt handler" guard. With Status at zero the guard fires every time, so every StartThread fails.

Dragon Quest VIII (SLUS-21207) hits this during boot. It creates its CD streaming thread, gets -1, prints Can't start thread for streaming. and then deadlocks every guest thread, none runnable, EeScheduler::waitForEvent in 10 of 10 stack samples. Nothing in the runtime logs anything, because from its point of view the guest asked a question and got an answer.

EIE matters for the matching reason: DIntr reports whether it was set so the caller knows whether to pair it with an EIntr. Starting at zero makes DIntr always answer "already disabled", so the re-enable never happens.

Two changes, both needed:

• R5900Context's constructor sets Status to EIE | IE instead of 0. BEV is deliberately left clear — that selects the boot exception vectors, which is the pre-handoff state, not this one.
• PS2Runtime's constructor no longer memsets m_cpuContext. R5900Context already zeroes itself before applying its reset values, so the memset only threw them away. Threads created later were unaffected, because EeScheduler::startThread assigns R5900Context{}, which is why this presented as "the main thread cannot start threads" rather than something more obviously global.

Verified on a fully recompiled retail binary: before, the streaming thread never starts; after, it does and boot proceeds to the next stage.

[ran-j]

Nice catch, almost ready to merge

[ran-j]

Can you reduce this long comment please

[ran-j]

here we dont need this comment