test: cover release funds balance flow

[dangelo352]

Summary

• add lifecycle coverage for validated and deadline release_funds paths with exact contract, creator, and success destination balance assertions
• add double-release rejection coverage proving balances are unchanged after the failed second release
• add funds_released event coverage for vault id and amount via env.events()
• document the new Issue Add full balance-flow test coverage for release_funds in tests/lifecycle.rs #226 release-flow coverage in the testing and coverage docs

Closes #226

Validation

• cargo fmt --check
• cargo test
• git diff --check

Note: local cargo tarpaulin --config tarpaulin.toml --out Stdout could not run because this environment does not have cargo-tarpaulin installed; the repository coverage workflow should run it in CI.

[1nonlypiece]

thanks for the work here — but our flow is that you need to be assigned to the issue before opening a PR for it. #226 isn't assigned to you, so i'm closing this as invalid for now. please claim #226 first (comment on the issue or grab it on the GrantFox board), then re-raise and we'll review right away. https://discord.gg/xvNAvMJf