feat(util-genai): auto-propagate common GenAI attributes via baggage

[fangxiu-wf]

Summary

Adds automatic propagation of the ARMS GenAI common attributes (gen_ai.agent.name / gen_ai.user.id / gen_ai.session.id) via OpenTelemetry Baggage, matching the Python loongsuite-otel-util-genai 0.6.1 behavior.

• startEntry / startInvokeAgent / startCreateAgent write the set common attributes into Baggage on the span's contextToken.
• GenAI child spans (LLM / Tool / ReAct Step / Embedding / Retrieval / Rerank / Memory) created under that context automatically inherit the three attributes — no need to set them on every child invocation.
• Fill-only: a child field is backfilled only when unset, so explicit values always win. Plain OTel SDK business spans are unaffected.
• Downstream (probe-created) spans can also read the values from baggage.
• New exported helpers setCommonBaggage / backfillCommonFromBaggage.
• Cleans up a dead no-op context.with(...) in TelemetryHandler.startLlm.
• Bumps to 0.1.0-beta.10.

Test plan

• npm run build (tsc) — clean
• npm test — 19 files / 207 tests passing (incl. new baggage-propagation.test.ts: child inheritance, explicit-wins, Entry propagation, no-baggage backward-compat)
• End-to-end verified against a real model (qwen): STEP/LLM/TOOL spans inherit agent.name/user.id/session.id without being set explicitly; custom business spans correctly do NOT inherit

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