feat(sdk): Add telemetry package to support sinks

[namrataghadi-galileo]

Summary

Added a new shared top-level telemetry/ package to hold common telemetry contracts and trace-context primitives used across AgentControl.

Refactored the SDK observability write path to use the shared ControlEventSink contract internally while preserving the existing default OSS behavior: queue-backed batching and delivery to /api/v1/observability/events.

Aligned telemetry packaging with the existing models/engine bundling pattern so telemetry is vendored into SDK and server builds rather than treated as a separate runtime-only dependency.

Scope

User-facing / API changes

• No intended user-facing behavior changes.
• No change to default OSS event delivery behavior.
• No new public sink-selection API in this story.

Internal changes

• Introduced shared telemetry types: ControlEventSink, SinkResult, BaseControlEventSink, and shared trace-context helpers.
• Removed SDK-local ownership of trace-context internals and pointed SDK code/tests to the shared telemetry package.
• Updated SDK observability internals so event writes flow through the shared sink contract.
• Updated build/package wiring so telemetry is bundled like models and engine.

Out of scope

• Server write-path refactor to the shared sink contract.
• Config-driven sink selection.
• OTEL sink implementation and OTEL settings.
• Any changes to /observability/events server ingestion behavior.

Risk and Rollout

Risk level: Medium

Rollback plan:

1. Revert the telemetry package introduction and SDK observability refactor.
2. Restore the previous SDK-local telemetry module and direct batcher-based event writes.
3. Remove telemetry vendoring from SDK/server build configuration.

Testing

• Added or updated automated tests
• Ran make check (or explained why not)

Focused validation is still pending locally; mypy surfaced follow-up packaging/type issues during development and we have been resolving those incrementally.

• Manually verified behavior

Checklist

• Linked issue/spec (if applicable)
• Updated docs/examples for user-facing changes

No docs/example updates were needed because this story is internal-only and no repo examples referenced the old telemetry module path.

• Included any required follow-up tasks

[codecov]

Codecov Report

❌ Patch coverage is 96.55172% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
sdks/python/src/agent_control/observability.py	96.00%	1 Missing ⚠️

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