OB-10135: propagate automate build id on observability buildStop

[darshan3881]

Summary

Cache the automate build hashed_id at build-create time and include it as automate_build_id on the observability-api buildStop payload (PUT /api/v1/builds/:id/stop).

Lets obs-api persist the mapping so the synergy (new) dashboard can call the railsApp /api/v1/cypress-builds/:id/resource-errors endpoint in the correct id-space directly, removing the OB-9830 reverse-lookup shim once end-to-end coverage is verified.

Payload change

Before:
```js
{ "stop_time": "..." }
```

After:
```js
{
"stop_time": "...",
"automate_build_id": ""
}
```

Purely additive — obs-api ingest declares automate_build_id as an optional typed field on BuildStopParams. Older ingest servers ignore unknown JSON keys (Jackson default), so this CLI change is safe to ship even before obs-api deploys.

Guarded by observability-session check

The new env var is only cached when isTestObservabilitySession is true (bin/commands/runs.js:341), and the payload change is only in stopBuildUpstream which is already o11y-gated. Non-o11y runs (customers with observability disabled) are unaffected.

Related

• Jira: OB-10135 (this) · OB-9830 (interim shim) · OB-9825 (FE parent)
• Spec: Confluence — OB-9830 + OB-10135 — section 12.3 row 1
• Consumer PRs:
  • obs-api read side: https://github.com/browserstack/observability-api/pull/8672
  • Frontend consumer: https://github.com/browserstack/frontend/pull/48305
  • Pipeline persistence: pending (obs-pipeline OB-10135-cypress-error branch)

Test plan

• node -c syntax check on both modified files
• Local run against staging obs-api once ingest DTO accepts the field
• End-to-end verification: run a real Cypress build → check obs-api's builds table has the new column populated after buildStop

Files changed

• bin/commands/runs.js (+5) — cache data.build_id into process.env.BROWSERSTACK_AUTOMATION_BUILD_ID inside the isTestObservabilitySession block
• bin/testObservability/helper/helper.js (+6/-1) — include automate_build_id in the stopBuildUpstream payload

Total: 2 files, +11/-1.