test: SML fixture is missing from clean checkouts

[thepastaclaw]

Missing SML fixture breaks clean test runs

Failure

npm test -- --run --passWithNoTests fails on main in
src/api/sml.test.ts before running that suite:

Error: ENOENT: no such file or directory, open '.../scripts/fixtures/sml-paloma-snapshot.bin'

Evidence

• Main CI failure:
  https://github.com/dashpay/dash-bridge/actions/runs/26610343045/job/78414619926
• Current upstream/main contains src/api/sml.test.ts but does not contain
  scripts/fixtures/sml-paloma-snapshot.bin.

Reproduction

git checkout main
npm ci
npm test -- --run --passWithNoTests

Diagnosis

The SML unit test eagerly reads scripts/fixtures/sml-paloma-snapshot.bin at
module load time. The fixture is not tracked in the repository, so the suite
fails with ENOENT on clean checkouts and in GitHub Actions.

[thepastaclaw]

Additional PR CI hit from #18:

• CI run: https://github.com/dashpay/dash-bridge/actions/runs/26611014420
• Failed job: build (20) https://github.com/dashpay/dash-bridge/actions/runs/26611014420/job/78416700420
• Failure: src/api/sml.test.ts eagerly reads missing scripts/fixtures/sml-paloma-snapshot.bin and fails with ENOENT before registering tests.

Scope check: this is not from PR #18's branch changes. The PR diff vs current upstream/main does not touch src/api/sml.test.ts, src/api/sml.ts, or scripts/fixtures/; I reproduced the same failure on a detached clean upstream/main worktree at 9378f88 with npx vitest --run src/api/sml.test.ts.