refactor: CustomScpTermination

[XingYeNotFish]

Refine and match corresponding DamageHandler

Description

Describe the changes
Refactored CustomScpTermination to align with the new CustomHandler type and DamageType enumeration, removed overly-restrictive CustomHandlerBase type checks, filled in all missing kill scenarios.

What is the current behavior? (You can also link to an open issue here)

• Missing messages for Scp Kill Scp, SCP-1507, and unknown death reason
• Potential NullReferenceException
• Messages do not match the actual DamageHandler(eg. MicroHidDamageHandler -> "TERMINATED BY AUTOMATIC SECURITY SYSTEM")

What is the new behavior? (if this is a feature change)

• Uses CustomDamageHandler exclusively; determines kill source via DamageType and Attacker
• Adds new text branches for Scp Kill Scp, SCP-1507, and unspecified kills
• Explicit null-check for info and Attacker to prevent exceptions

Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
Yes — method signature changed from CustomHandlerBase to CustomHandler; any external callers must update their references.
(Impact is zero if the entire codebase already uses CustomHandler.)

Other information:

• Glitchy effect parameters (GlitchyMessage glitchChance/jamChance) remain unchanged
• No Harmony patches or IL modifications required

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentations

Submission checklist

• I have checked the project can be compiled
• I have tested my changes and it worked as expected

Patches (if there are any changes related to Harmony patches)

• I have checked no IL patching errors in the console

Other

• Still requires more testing

[louis1706]

Breaking change