CCL allreduce: rename to lrab_hierarchical_allreduce + descriptive plots

Rename the intercube all-reduce identity to lrab_hierarchical_allreduce
(module, config key, distributed test) so the name reflects both levels
it implements: LRAB intra-SIP (local reduce to center root + broadcast)
and the hierarchical inter-SIP topology exchange (ring/torus/mesh).
ADR-0032 slug kept as the stable decision id; pure rename, no logic change.

Also in this batch:
- ADR-0032 (EN+KO): document the shipped center-root bidirectional reduce
  (doc was stale corner-root); annotate ccl.yaml root_cube as a placeholder.
- Rename allreduce + pe2pe latency plots to descriptive, title-matching
  filenames and retitle the in-plot headings; drop overview/overview_log.
- Point the PPTX image refs at the new plot names.

Doc + derived-artifact + rename only; no simulation behavior changed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_intercube_root_center.py

@@ -1,7 +1,7 @@
-"""Phase 1 test for moving the intercube_allreduce root cube from the
+"""Phase 1 test for moving the lrab_hierarchical_allreduce root cube from the
 bottom-right corner (3,3) to the geometric center (2,2).
 
-Today's algorithm (intercube_allreduce.py) hardcodes
+Today's algorithm (lrab_hierarchical_allreduce.py) hardcodes
 ``root_cube = (cube_h-1) * cube_w + (cube_w-1)`` (= cube 15 in 4×4).
 The intra-SIP critical path for one allreduce is therefore::
 
@@ -55,7 +55,7 @@ def _run_torus_96kb(tmp_path: Path) -> float:
         sub,
         sip_topology="torus_2d",
         n_sips=6,
-        algorithm="intercube_allreduce",
+        algorithm="lrab_hierarchical_allreduce",
         sip_w=3, sip_h=2,
         n_elem_override=49152,   # 49152 × 2 = 96 KB / slot
     )
@@ -70,7 +70,7 @@ def _run_torus_96kb(tmp_path: Path) -> float:
     ) as ctx:
         result = run_allreduce(
             ctx, engine, spec,
-            algorithm="intercube_allreduce", ccl_yaml=ccl_path,
+            algorithm="lrab_hierarchical_allreduce", ccl_yaml=ccl_path,
         )
         assert result["ok_cubes"] > 0
     pe_exec_vals = [
@@ -121,7 +121,7 @@ def test_correctness_preserved(tmp_path):
         sub,
         sip_topology="torus_2d",
         n_sips=6,
-        algorithm="intercube_allreduce",
+        algorithm="lrab_hierarchical_allreduce",
         sip_w=3, sip_h=2,
         n_elem_override=128,   # tiny payload to keep this fast
     )
@@ -136,7 +136,7 @@ def test_correctness_preserved(tmp_path):
     ) as ctx:
         result = run_allreduce(
             ctx, engine, spec,
-            algorithm="intercube_allreduce", ccl_yaml=ccl_path,
+            algorithm="lrab_hierarchical_allreduce", ccl_yaml=ccl_path,
         )
     n_cubes = 6 * 16  # 6 SIPs × 16 cubes/SIP
     assert result["ok_cubes"] == n_cubes, (