Allow parent spans to display logs from all child spans within the trace hierarchy

### Problem Statement

Currently, when viewing a span in the trace view, the Logs panel only shows entries emitted directly within that span (trace.parent_span_id = span ID). Logs from nested or child spans do not appear in the parent’s Logs panel, making it difficult to view a complete picture of activity for an endpoint or transaction with multiple sub-operations.

### Solution Brainstorm

When a user selects a parent span, automatically include logs from all descendant spans in the Logs panel.
To make this clear:
- Visually differentiate direct vs. inherited logs.
- Optionally include a toggle (“Show logs from child spans”).

### Product Area

Explore

Start in the Explore trace view and inspect how the Logs panel currently filters entries to the selected span. Define how descendant spans are identified, how direct and inherited logs are distinguished, and whether a child-log toggle is needed; done means selecting a parent shows the agreed logs from its trace hierarchy.

Written by the indexing model from the issue text.