feat(sensor): add opt-in OpenTelemetry log export

[barisozbas]

Summary

Intent:

• Let Sensor users forward normalized records to SIEM pipelines without changing default behavior.
• Keep export explicitly opt-in and preserve complete parser output without exporter-side redaction.

Changes:

• Add validated JSON configuration and an optional OTLP/HTTP dependency extra.
• Emit agent sessions and system configurations as OpenTelemetry logs during the existing one-shot run.
• Flush before exit, surface endpoint failures, and document configuration, deduplication, and privacy behavior.

Test Plan

• Sent an AgentEvent to a local OTLP/HTTP receiver and decoded the full unredacted protobuf payload.
• Verified a base installation runs without OpenTelemetry packages and gives install guidance when export is enabled.

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Issues