Add support for tracing contract metadata through multi-contract invocation chains

[pugsley76]

Description:
Glassbox should preserve and display metadata across multi-contract invocation chains when a transaction calls multiple contracts.

Work to be done:
Extend trace models to carry contract metadata through nested invocations.

Implementation procedure:

1. Update trace node structures to include contract metadata along contract call chains.
2. Propagate metadata through nested invocation flows.
3. Display metadata in viewers and exports.
4. Add tests for metadata propagation.
5. Document the feature.

Acceptance criteria:

• Contract metadata is preserved through nested invocations.
• Trace viewers show metadata at each call boundary.
• Tests verify propagation.
• Documentation explains the metadata flow.

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