feat: deallocate allocations on settlement

[dangelo352]

Summary

• add a CommitmentCore-authorized allocation_logic::deallocate entrypoint that clears allocation records and decrements pool liquidity
• invoke deallocation from commitment_core settle and early_exit when an allocation contract is configured
• document the settlement/early-exit deallocation lifecycle

Tests

• CARGO_TARGET_DIR=/tmp/commitlabs-deallocate-target cargo test -p allocation_logic deallocate -- --nocapture
• CARGO_TARGET_DIR=/tmp/commitlabs-deallocate-target cargo test -p commitment_core deallocate -- --nocapture
• git diff --check

Closes #468