docs(reference): add DepthReductionCompressor cross-reference to skeleton_compressor (v3.8.0)

docs/reference/skeleton_compressor.md

@@ -11,6 +11,14 @@ The compressor lives in
 `cleveragents.application.services.skeleton_compressor.SkeletonCompressorService`
 and is registered in the DI container as `skeleton_compressor_service`.
 
+> **v3.8.0+:** The ACMS pipeline's Phase 3 `SkeletonCompressor` slot is now
+> filled by `DepthReductionCompressor`, which re-renders fragments at lower
+> UKO detail depths rather than dropping them.  `SkeletonCompressorService`
+> (this document) handles the `skeleton_ratio` budget policy and is a
+> separate component.  See
+> [Depth Reduction Compressor](../modules/depth-reduction-compressor.md)
+> for the pipeline-integrated compressor.
+
 ## Skeleton Ratio
 
 | Ratio | Meaning | Behaviour |
@@ -107,3 +115,9 @@ compressed fragments as the child's inherited context budget.
 The `--skeleton-ratio` flag on `agents project context set` sets the
 ratio for a project's context policy.  The `plan status` command
 displays the compression summary when `skeleton_metadata` is present.
+
+## See Also
+
+- [Depth Reduction Compressor](../modules/depth-reduction-compressor.md) —
+  production ACMS pipeline compressor that re-renders fragments at lower
+  UKO detail depths (v3.8.0+)