M_CPU/SRAM placement via pos_mm in topology.yaml (nearest router)

Component placement uses mm coordinates in topology.yaml, mesh_gen
finds the nearest router automatically. M_CPU moved to pos_mm=[7.5,2.0]
(→ r0c2), SRAM at pos_mm=[1.5,9.0] (→ r3c0).

No hardcoded router references in topology config.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

topology.yaml

@@ -95,6 +95,11 @@ cube:
     hbm_ctrl:   { kind: hbm_ctrl, impl: hbm_ctrl_v1, attrs: { capacity: 1, efficiency: 1.0 } }
     sram:       { kind: sram,     impl: sram_v1,     attrs: { size_mb: 32, overhead_ns: 2.0 } }
 
+  # Physical placement of non-PE components (mm coordinates)
+  placement:
+    m_cpu:  { pos_mm: [7.5, 2.0] }   # top center area, near UCIe-N
+    sram:   { pos_mm: [1.5, 9.0] }   # left side, below HBM zone
+
   ucie:
     decompose: true
     ports: [N, S, E, W]