Improve documentation of the Clear archetype (#4760)

### What

* Fixes #4143

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crates/re_types/definitions/rerun/archetypes/clear.fbs

@@ -9,6 +9,14 @@ namespace rerun.archetypes;
 
 /// Empties all the components of an entity.
 ///
+/// The presence of a clear means that a latest-at query of components at a given path(s)
+/// will not return any components that were logged at those paths before the clear.
+/// Any logged components after the clear are unaffected by the clear.
+///
+/// This implies that a range query that includes time points that are before the clear,
+/// still returns all components at the given path(s), except those logged directly before the clear.
+/// Meaning that in practice clears are ineffective for time series plots and other usages of visible time ranges.
+///
 /// \example clear_simple title="Flat" image="https://static.rerun.io/clear_simple/2f5df95fcc53e9f0552f65670aef7f94830c5c1a/1200w.png"
 /// \example clear_recursive !api "Recursive"
 table Clear (