D-10: skip SIF CMD teardown before embedded loader handoff on non-reset IOP

[Copilot]

HDD-backed POPSTARTER.ELF black-screens because ExecuteViaEmbeddedLoader calls SifExitCmd() unconditionally before ExecPS2(loader) — even on HDD paths where the IOP was never reset. SifExitCmd() sends a terminate packet to the IOP's SIF CMD handler, putting it in "waiting-for-re-init" state. The embedded loader starts with a zeroed .bss, calls SifInitRpc(0) → SifInitCmd() → SifSendCmd(SIF_CMD_INIT_CMD, ...), and waits for an IOP acknowledgment that never arrives. Permanent hang.

Root cause

ExecuteViaEmbeddedLoader applies the same SifExitIopHeap / SifExitRpc / SifExitCmd teardown regardless of whether the IOP was reset. For non-HDD reboot paths this is fine — prepare_reboot_exec_environment() already reset the IOP before this point. For HDD-backed paths the IOP is still running with all modules loaded, and terminating its SIF CMD handler breaks the loader's ability to re-establish RPC.

Consistent with DECISIONS.md line 101 ("the embedded-loader boundary only became stable once EE-side SIF teardown before ExecPS2 was removed") and with reference launchers (wLaunchELF) that do not call SifExitCmd before their embedded loader on a non-reset IOP.

Change

src/elf_loader/src/elf.c — gate SIF teardown on IOP-reset status:

/* SifExitCmd() terminates the IOP SIF CMD handler. On a non-reset IOP
 * this prevents the loader's SifInitRpc(0) from completing.
 * Non-HDD paths go through prepare_reboot_exec_environment() first
 * (IOP already reset), so the full teardown is correct there.
 */
if (!is_hdd_backed_exec_path(partition_context)) {
    SifExitIopHeap();
    SifExitRpc();
    SifExitCmd();
}
FlushCache(0);
FlushCache(2);
ret = ExecPS2((void *)boot_header->entry, 0, final_argc, launch_argv);

• Non-HDD reboot paths: teardown unchanged.
• HDD-backed paths: teardown skipped; IOP SIF CMD handler stays active; loader's SifInitRpc(0) gets an immediate IOP response.

Docs

DECISIONS.md, STATE.md, ROADMAP.md, README.md, QA_REGRESSION_MATRIX.md updated. Hardware result marked Unknown (verify on hardware).