fix(engine): add player-counter Ward cost for "Get five poison counters" - #6662

This PR adds support for a new player-counter Ward cost variant ("Get five poison counters") in a Magic: The Gathering game engine. The scan reviewed 27 changed files across the engine, AI policy, client UI, and test suites.

CI/CD: No workflow files, Docker files, or CI configuration were changed. The ci-cd-security skill was not triggered.

Lifecycle events: No package-manager hooks, build scripts, entrypoints, or startup code were changed. No Cargo.toml, build.rs, npm scripts, setup.py, or git hooks present in the diff.

Malicious intent: No indicators found. The changes introduce no network calls, telemetry, credential handling, obfuscation, encoded payloads, dangerous eval/exec patterns, or binary/blob additions. All code follows existing patterns in the repository, is extensively commented, and includes integration and unit tests. The parser change is a security-positive bug fix that fails closed on malformed Ward cost text instead of silently producing a free, always-paid Ward.

Skill mutations: No materialized skill target directories were listed (skill-targets.json is []). The skill-security scanner was not triggered.