fix: make workflow stop not-found message explicit + add npm test script

[bart-btom-oss]

Summary

• ensure not-found responses for workflow status/stop always include the user query (even when there are zero runs)
• add npm test script to standardize local/CI validation (build + Node test runner)

Why

• baseline tests exposed a failing expectation: non-existent run message omitted the queried id when run history was empty
• repository had tests but no package test script

Validation

• npm ci
• npm run build
• npm test

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