feat(otel): propagate parent span ID through aw_context for cross-job trace hierarchy

[Copilot]

Child workflow setup spans were sent with no parentSpanId, causing multi-job dispatch traces to appear as disconnected root spans in every OTel backend instead of a properly nested tree.

Changes

• aw_context.cjs — buildAwContext() now includes otel_parent_span_id from GITHUB_AW_OTEL_PARENT_SPAN_ID, mirroring the existing otel_trace_id / GITHUB_AW_OTEL_TRACE_ID propagation
• send_otlp_span.cjs — sendJobSetupSpan reads awInfo.context.otel_parent_span_id and passes it as parentSpanId to buildOTLPPayload, linking the child setup span under the parent's setup span
• send_otlp_span.test.cjs — three new tests covering valid propagation, absent field, and invalid span ID rejection

Result

Child job setup spans in dispatched workflows now carry the parent job's span ID:

// Before: child setup span is a disconnected root
{ traceId: "<parent_trace_id>", spanId: "<child_span_id>" }

// After: child setup span is properly nested
{ traceId: "<parent_trace_id>", spanId: "<child_span_id>", parentSpanId: "<parent_span_id>" }

[Copilot]

Pull request overview

This PR fixes cross-workflow trace hierarchy in OTLP by propagating the parent job’s setup span ID through aw_context and using it as parentSpanId for dispatched child workflow setup spans, so traces render as a single nested tree instead of disconnected roots.

Changes:

• Add otel_parent_span_id to aw_context (sourced from GITHUB_AW_OTEL_PARENT_SPAN_ID) to propagate the parent setup span across workflow dispatch boundaries.
• Update sendJobSetupSpan to read aw_info.context.otel_parent_span_id, validate it, and pass it to buildOTLPPayload as parentSpanId.
• Add tests to verify valid propagation, omission when absent, and omission when invalid.

Show a summary per file

File	Description
actions/setup/js/aw_context.cjs	Extends dispatched aw_context with otel_parent_span_id to carry parent setup span ID to child workflows.
actions/setup/js/send_otlp_span.cjs	Uses propagated otel_parent_span_id (when valid) as parentSpanId on the child job setup span payload.
actions/setup/js/send_otlp_span.test.cjs	Adds coverage for propagation/absence/invalid cases for otel_parent_span_id → parentSpanId.

Copilot's findings

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• Files reviewed: 3/3 changed files
• Comments generated: 0