Failed EPR transition leaves hard throttle asserted and latches the port until physical AC removal #3

Both EPR failure handlers leave the transition throttle event set; the normal release only clears it when AC power exceeds 100W, which cannot hold after a failed EPR entry. The epr_active = 0xff no-retry marker is cleared only on a port-disconnect response, so it survives missed disconnect events and PD controller resets (EC RAM re-imposes it). Result: system-wide slow state (BIOS included) and/or a port stuck attach-without-contract, recoverable only by unplugging AC.

Tracking + evidence: tyeth/framework-system#1
Proposed minimal fix: #1