Add regression coverage for mismatched fluid/item IO warning pairs

[Copilot]

This issue asks for warnings when IO resource kinds are unpaired (e.g., INPUT fluid with default item OUTPUT, and vice versa). The linter logic already implements this behavior; this PR adds targeted coverage for the exact reported scenario.

• What changed

  • Added a new migrated gametest:
    • UnusedIoWarningMismatchedItemAndFluidResourceKindsGameTest
  • The test program intentionally mixes resource kinds in one trigger:
    • INPUT fluid:: FROM left
    • OUTPUT TO left (defaults to item)
  • Assertions verify both warnings are emitted in the same run:
    • output resource kind missing from inputs (sfm:item)
    • input resource kind never consumed by outputs (sfm:fluid)

• Why this matters

  • Locks in expected warning behavior for the specific mismatch pattern discussed in the issue.
  • Prevents regressions without changing production linting logic.

EVERY 20 TICKS DO
    INPUT fluid:: FROM left
    OUTPUT TO left
END