Add Trust shared trace schema

[GsCommand]

Motivation

• Restore the previous Commons trace envelope into the Trust shared schema folder so Trust consumers have a shared trace type for correlation.
• Update schema metadata to point to the Trust namespace and label the schema for CLAS while preserving the original field structure and constraints.

Description

• Added schemas/trust/_shared/trace.schema.json containing the trace envelope using draft 2020-12 and additionalProperties: false.
• Set $id to https://schemas.commandlayer.org/schemas/v1.0.0/trust/_shared/trace.schema.json and changed title to CLAS Trace with the requested description text.
• Preserved the original fields and constraints: required trace_id only, optional span_id, parent_span_id, timestamp, and tags, with maxLength: 128 for identifiers, timestamp as date-time, and tags values as strings with maxLength: 512.
• Did not change field structure or other validation rules from the Commons schema.

Testing

• Ran jq . schemas/trust/_shared/trace.schema.json to validate JSON syntax which succeeded.
• Verified repository status with git status --short and committed the new file which succeeded.
• No failing automated schema validations were produced during the change.

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Codex Task