ci: wire verify-contracts into CI and add rounding edge case tests

[Onyii1234]

• [Chore] Wire verify-contract-addresses.ts into CI #431: add verify-contracts CI job to ci.yml

  • uses dorny/paths-filter@v3 to gate on constants.ts / known-pools.ts
  • installs Stellar CLI and wasm32v1-none target (matching script's expected build path)
  • delegates retry logic to the existing retry() in the script itself
  • job is required/blocking; skips expensive steps on unrelated PRs

• [Test] Add coverage for DepositTooSmall and WithdrawalTooSmall rounding edge cases #434: add DepositTooSmall and WithdrawalTooSmall test coverage

  • deposit_too_small_fails: seeds 1-stroop deposit, inflates share price via direct adapter donation, asserts 1-stroop deposit returns ContractError::DepositTooSmall
  • withdrawal_too_small_fails: seeds 1-stroop deposit, drains adapter balance to zero, asserts withdrawal returns ContractError::WithdrawalTooSmall
  • cargo test -p meridian-vault: 26/26 pass

Summary

Test plan

• pnpm lint && pnpm typecheck && pnpm test pass locally
• [ ]

Closes #431
closes #434

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[collinsezedike]

This needs to be split into two PRs before it can be reviewed further. Please read CONTRIBUTING.md, specifically the "Pull Request Process" section, rule 1: "One PR per issue. Do not bundle multiple issues into a single PR." This one closes both #431 and #434 with unrelated changes, a CI workflow job and Rust contract tests. Please open one PR for each.

CI is also failing: cargo fmt --check fails on a missing trailing newline at the end of vault/src/lib.rs. Run cargo fmt and push the result.

The PR body's ## Summary and ## Test plan sections are empty, the actual template placeholders are still there unfilled. Please also read the "PR body format" section of CONTRIBUTING.md, the content you wrote above the template is detailed and useful, it just needs to go in the right place.

The underlying work in both changes looks solid otherwise, the CI job is correctly scoped and the rounding tests are well-reasoned. Once split, fixed, and the body filled in properly, this should move quickly.