feat(tracing): delegate obs edge to sgp-obs + wire init_tracing at ACP startup

[NiteshDhanpal]

What

Moves the SDK's inline observability edge (the correlation/wrapper-span/temporal-interceptor work from #484/#485/#490/#491) out into the shared sgp-obs library, so the SDK just delegates. Net diff vs main is the delegated implementation — the intermediate inline code (added in the #484/#485/#491 commits, which were never merged to main) is replaced by thin shims.

• obs_ids.py / obs_span.py / temporal.py / trace.py — delegate correlation, the per-step wrapper span, the begin-obs wrapper-vs-ambient decision, and the Temporal interceptors to sgp_obs.traces backends + Correlator.
• adk/pyproject.toml — add sgp-obs==0.2.0rc1; root pyproject.toml — add the CodeArtifact scale index + an explicit source (published wheel just pins the version; consumers resolve from their own index/PyPI).
• base_acp_server.py — wire sgp_obs.traces.init_tracing() into the ACP lifespan.

Why init_tracing matters

Without it, get_tracer() resolves to the API-default ProxyTracerProvider: obs wrapper spans never record or export. The forward edge (obs ids in business-span metadata) still fills from ambient/propagated W3C context, but no obs span carrying the <source>.business_trace_id reverse anchor ever reaches the collector, so the business→obs pivot has nothing to land on. init_tracing adopts an app-installed provider if present, else installs one with the OTLP exporter. Fail-open (never raises out of startup).

Validation (sgp-dev, rocket-mock + audit)

• Agent registers and serves; no crashloop.
• 20/20 business spans correlate — obs ids in span metadata, 0 nulls.
• With init_tracing, per-step wrapper spans record (distinct span ids, not a reused ambient context) and carry agentex.business_trace_id / agentex.business_span_id.
• force_flush to the OTLP collector returns True (spans ship).

🤖 Generated with Claude Code

Greptile Summary

The PR delegates observability correlation, wrapper spans, streaming instrumentation, and Temporal propagation to sgp-obs, while initializing tracing during ACP startup.

• Adds the sgp-obs dependency and private-index resolution configuration.
• Integrates tracing across ACP ingress, Temporal clients and workers, LLM streams, and span processors.
• Replaces the previous inline correlation implementation and its implementation-specific tests with delegated backends and lifecycle coverage.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
src/agentex/lib/core/tracing/trace.py	Delegates correlation and wrapper-span lifecycle to sgp-obs, adds bounded handle tracking, and makes processor and queue failures fail-open.
src/agentex/lib/sdk/fastacp/base/base_acp_server.py	Adds inbound trace-context middleware and initializes the shared tracing provider during ACP lifespan startup.
src/agentex/lib/core/tracing/temporal.py	Provides the environment-controlled shim for delegated Temporal tracing interceptors.
src/agentex/lib/core/temporal/workers/worker.py	Installs delegated tracing interceptors on Temporal client and worker boundaries.
src/agentex/lib/core/adapters/llm/_stream_obs.py	Centralizes defensive stream extraction and GenAI span attributes for both LLM gateways.
adk/pyproject.toml	Adds the shared sgp-obs tracing dependency used by the delegated implementation.
tests/lib/core/tracing/test_obs_ids.py	Removes tests tied to deleted inline correlation helpers, resolving the previously reported test failure.

Sequence Diagram

sequenceDiagram
    participant C as ACP Client
    participant A as ACP Server
    participant O as sgp-obs
    participant T as Temporal
    participant W as Worker/Activity
    participant P as Span Processors
    C->>A: Request with traceparent
    A->>O: Continue inbound context
    A->>O: Initialize tracing provider
    A->>T: Start workflow or send signal
    T->>W: Propagate OTel context
    W->>O: Open correlated wrapper span
    W->>P: Persist business span
    O-->>O: Export observability span

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Context used (5)

• Knowledge Base — AgentEx tracing and observability
• Knowledge Base — AgentEx execution lifecycle in Temporal
• Knowledge Base — FastACP server framework
• Knowledge Base — Agent execution harness
• Knowledge Base — AgentEx ADK runtime and services