test(sdk): bind LocalKVStore setup to its declared fixture variable

[Quaakee]

Program and scope

LocalKVStore fixture setup assigned to an undeclared pushDropInstance even though its variable was named _pushDropInstance. Node26 rejected nine tests; Node24 tolerated the implicit global. Both assignments now use the declared variable, preserving mock construction and every assertion.

• Tracker: project-at-las/Atlas-Documentation#529
• Exact independently reviewed head:402bc1e519e30ce8e46a46454011c0d564e118e2
• Test-only repair; no runtime/package/API/manifest/dependency change.

Impact

• No public package source or manifest changed (only test fixtures)
• Affected package: @bsv/sdk test suite; no published-byte change or version bump.

Verification

• Node24.18.0 fullSDK coverage:160suites,5992tests pass.
• Node24 and Node26 focused LocalKVStore fixture:14/14pass each.
• SDK lint/typecheck/format, packed consumers, browser budgets, property tests, license checks and Node24 repositoryhealth pass.
• All three package builds remain identical: SHA256af773c7f5e6dc685e16e4623c1cb9ba6da115051c1db354cb00cb43acc215d4b.
• Audit passed existing policy with2moderate findings and2ignoredhigh findings; not a clean vulnerability inventory.
• Fresh independent source review returned no source/package findings; associated provenance doc finding resolved separately in Atlas docs.
• Complete diff reviewed for correctness, compatibility and unchanged package bytes.
• Hosted checks are terminal and successful (pending).

Security and dependencies

• No dependency or lockfile change.
• No new override, suppression, skipped test, budget, expiry date or gate change.
• Exact-head hosted CodeQL/Sonar analysis complete (pending).

Release and operations

• No npm publication from workstation or this PR.
• No public-byte change; package version and release notes intentionally unchanged.
• No image/deployment/storage impact.
• No migration needed. This is the maintained Quaakee fork, not an upstream BSV release.

Completion evidence

Hosted CI will be observed on this exact head before merge; the PR remains draft while pending. Atlas package consumption and both-relay qualification are tracked separately and are not accepted by this fixture correction.