[SrMessiSOL]

What changed

• reject alliance leave or expel operations for inactive membership records
• decrement the alliance member count exactly once for active members
• add regression coverage for active and inactive membership deactivation

Root cause

Alliance membership accounts remain allocated after leave or expulsion with role 0. The handlers did not require an active role, so the same account could repeatedly decrement member_count.

Impact

Prevents alliance capacity and membership accounting from being corrupted by replaying leave or expel operations.

Validation

• cargo test --workspace --lib --locked
• focused membership deactivation regression tests
• git diff --check