refactor: use ui messages for skill status

[3vcloud]

Replace StoC terminal skill-state handling with the client UI broadcasts introduced in GWCA 4.8.6.0.

• Track cancelled skills through kAgentSkillCancelled.
• Track interrupted skills through kAgentSkillInterrupted.
• Remove duplicate StoC stopped/interrupted handling from Observer.
• Render cancelled and interrupted Skill Monitor entries separately.

[RiftLurker]

I don't think this is correct, now it's marking cancelled skills as interrupted instead.

[3vcloud]

yep, looks like the game isn't even following its own logic atm - both are interrupts