feat!: rename track_latency to track_duration on AIGraphTracker

[jsonbailey]

Summary

• Rename AIGraphTracker.track_latency() → track_duration() to align with the updated AIGRAPHTRACK spec
• Update the event key from $ld:ai:graph:latency → $ld:ai:duration:total
• Update all call sites in OpenAI and LangChain provider packages and their tests

Test plan

• All server-ai unit tests pass (115 tests)
• All langchain provider tests pass (81 tests)
• All openai provider tests pass (39 tests)
• No remaining references to track_latency or $ld:ai:graph:latency in the codebase

🤖 Generated with Claude Code

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Note

Medium Risk
Breaking API/event-name change for telemetry: downstream callers and dashboards relying on track_latency/$ld:ai:graph:latency must migrate to the new method and event key.

Overview
Updates graph-level tracking to report duration instead of latency by renaming AIGraphTracker.track_latency() to track_duration() and changing the emitted event from $ld:ai:graph:latency to $ld:ai:graph:duration:total.

All LangGraph and OpenAI agent graph runners (and their unit/integration tests) are updated to call the new method and assert on the new event key for both success and failure paths.

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