[iterate-2G] db16cyc spin-hint cooperative yield: unblock title-screen 0x10a0 gate

The silph title state machine (tid13) blocked on event 0x10a0, never signaled.
Root: the event's producer chain runs on the silph worker (entry 0x821C4AD0,
our tid14), which was starved. tid14 shares a HW slot with a guest spinlock/
barrier participant (sub_824D1328, entry 0x824D2940) that busy-spins on the
db16cyc hint `or r31,r31,r31` (encoding 0x7FFFFB78) at 0x824D140C. Under our
round-robin lockstep the spinner consumed its whole block every round and
starved the co-located tid14 (only 9 progress hits over 200M instr) — so the
producer never reached the event-create/duplicate/signal dance the canary
oracle performs (handle F80000E8 set by the submitter F8000044 via a duplicated
handle).

Fix (canary-faithful): recognize the db16cyc spin hint exactly as canary's
InstrEmit_orx does (code 0x7FFFFB78 -> DelayExecution) and surface it as a new
StepResult::Yield. The scheduler's yield_current() promotes every Ready peer on
the slot past STARVE_LIMIT so begin_slot_visit picks one next round, then they
reset and the spinner reclaims the slot — fair alternation, no priority
inversion, pure function of slot state (deterministic).

Result (lockstep, cache-persist, -n 200M): tid14 progresses past its old stall
into a real wait; tid13 advances off 0x10a0 to a new event; hub/submitter
re-enter their wait loops. imports 280k->592k, packets 124M->164M, swaps 1->2.
draws still 0 (the splash's first draw is a further-upstream gate).

Determinism preserved (two cold n50m runs byte-identical). n50m golden
re-baselined (imports 90296->339766, swaps 1->2; draws unchanged 0). n2m
golden unchanged (db16cyc not reached in first 2M). Tests 670/670.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

audit-runs/audit-059-handle-disambiguation/round27-state-advance/disasm-sub82451238.txt

@@ -0,0 +1,80 @@
+  0x82451238:  mflr    r12
+  0x8245123c:  li      r0, 0
+  0x82451240:  stw     r0, 4(r1)
+  0x82451244:  bl      0x825F0F80
+  0x82451248:  subi    r31, r1, 160
+  0x8245124c:  stwu    r1, -160(r1)
+  0x82451250:  mr      r30, r4
+  0x82451254:  li      r9, 1
+  0x82451258:  lwz     r10, 32(r30)
+  0x8245125c:  stw     r30, 188(r31)
+  0x82451260:  stw     r9, 8(r30)
+  0x82451264:  cmplwi  cr6, r10, 0x0
+  0x82451268:  beq     cr6, 0x82451288
+  0x8245126c:  lwz     r11, 4(r30)
+  0x82451270:  lwz     r8, 4(r10)
+  0x82451274:  cmplw   cr6, r11, r8
+  0x82451278:  bne     cr6, 0x82451288
+  0x8245127c:  mr      r11, r9
+  0x82451280:  li      r26, 0
+  0x82451284:  b       0x82451290
+  0x82451288:  li      r26, 0
+  0x8245128c:  mr      r11, r26
+  0x82451290:  clrlwi  r11, r11, 24
+  0x82451294:  cmplwi  cr6, r11, 0x0
+  0x82451298:  beq     cr6, 0x824512A0
+  0x8245129c:  stw     r9, 8(r10)
+  0x824512a0:  lwz     r3, 36(r30)
+  0x824512a4:  lwz     r11, 0(r3)
+  0x824512a8:  lwz     r11, 32(r11)
+  0x824512ac:  mtctr   r11
+  0x824512b0:  bctrl
+  0x824512b4:  mr      r27, r3
+  0x824512b8:  stw     r26, 84(r31)
+  0x824512bc:  stw     r27, 96(r31)
+  0x824512c0:  bl      0x82454498
+  0x824512c4:  addi    r4, r31, 84
+  0x824512c8:  bl      0x82454580
+  0x824512cc:  stw     r26, 92(r31)
+  0x824512d0:  addi    r11, r27, 2047
+  0x824512d4:  lis     r10, 0x2
+  0x824512d8:  clrrwi  r11, r11, 11
+  0x824512dc:  cmplw   cr6, r11, r10
+  0x824512e0:  stw     r11, 100(r31)
+  0x824512e4:  ble     cr6, 0x824512F4
+  0x824512e8:  lis     r11, 0x8207
+  0x824512ec:  addi    r11, r11, 6724
+  0x824512f0:  b       0x824512F8
+  0x824512f4:  addi    r11, r31, 100
+  0x824512f8:  addi    r3, r31, 84
+  0x824512fc:  lwz     r4, 0(r11)
+  0x82451300:  bl      0x82454B08
+  0x82451304:  mr      r8, r8
+  0x82451308:  mr      r28, r3
+  0x8245130c:  stw     r28, 92(r31)
+  0x82451310:  b       0x82451324
+  0x82451314:  lwz     r30, 188(r31)
+  0x82451318:  lwz     r27, 96(r31)
+  0x8245131c:  li      r26, 0
+  0x82451320:  lwz     r28, 92(r31)
+  0x82451324:  addi    r3, r31, 84
+  0x82451328:  bl      0x82454AA0
+  0x8245132c:  mr      r29, r3
+  0x82451330:  cmplwi  cr6, r28, 0x0
+  0x82451334:  beq     cr6, 0x82451684
+  0x82451338:  lwz     r3, 36(r30)
+  0x8245133c:  li      r8, 0
+  0x82451340:  addi    r7, r31, 88
+  0x82451344:  mr      r6, r29
+  0x82451348:  mr      r5, r29
+  0x8245134c:  mr      r4, r28
+  0x82451350:  lwz     r11, 0(r3)
+  0x82451354:  lwz     r11, 28(r11)
+  0x82451358:  mtctr   r11
+  0x8245135c:  bctrl
+  0x82451360:  clrlwi  r11, r3, 24
+  0x82451364:  cmplwi  cr6, r11, 0x0
+  0x82451368:  beq     cr6, 0x82451684
+  0x8245136c:  lwz     r11, 28(r30)
+  0x82451370:  rlwinm  r11, r11, 0, 28, 28
+  0x82451374:  cmplwi  cr6, r11, 0x0