Fix Zed swap's unprinted exhaust cost

[abueide]

Problem

Zed, Without a Sound's Action swap charges one Energy and one Chaos Power, but no Exhaust cost. Its bare activated ability inherited SelfCost::Auto, which exhausts unit sources. An existing test incorrectly treated the Action arrow as an Exhaust cost.

Change

• Give only this swap an explicit SelfCost::Free; preserve Action timing and printed resource costs.
• Cover ready and exhausted Zed, repeat activation, resource failure/cancellation atomicity, and invalid Clone locations.
• No global activation-default, wire, blob, or snapshot changes.

Card reference: https://playriftbound.com/en-us/card-gallery/#card-gallery--ven-112-166

Validation

• Focused Zed tests: 6 passed in each rules repository.
• Full turns library: Agni 4,580 passed / 172 ignored; agni-rfb 4,566 passed / 172 ignored.
• cargo fmt --all -- --check, pinned Nix treefmt --ci, and bash ci/check.sh passed in both repositories.
• Ignored tests are not counted as verified. No live Kai/GUI or network playtest claimed.

Integration

The implementation is mirrored because Kai still consumes the Agni copy. A companion repository PR is linked separately. Merging this rules change alone does not update an existing Kai dependency pin or running module session.

[abueide]

Mirrored rules PR: abysl/agni-rfb#1 . Kai integration will pin the combined audit fixes; no main branch has been merged by this task.