Improve death-drain creature evaluation

[Rauglothgor]

Problem

When choosing creature removal targets, the AI can prefer a one-shot death trigger such as Serrated Scorpion over repeatable death-drain engines such as Zulaport Cutthroat, Blood Artist, and Cruel Celebrant.

Fixes #4171.

Minimal Fix

Creature evaluation now adds a small value bump for dies triggers that:

• move from battlefield to graveyard,
• include Other in ValidCard, and
• execute a LoseLife ability.

This keeps self-only death triggers such as Serrated Scorpion from receiving the same repeatable-engine value.

Validation

• JAVA_HOME=/home/rauglothgor/.local/codex-tools/jdk17 /home/rauglothgor/.local/codex-tools/apache-maven-3.9.9/bin/mvn -pl forge-ai -am -DskipTests compile
• Build succeeded with 0 checkstyle violations.

Known Limits

This is not a general trigger evaluator. It only covers the narrow repeatable death-drain case described in the issue.

AI Assistance Disclosure

I used AI assistance to inspect the issue, trace the target-evaluation path, make the narrow change, and run validation. I reviewed the final diff and validation before opening this PR.