analytical-viz: default intra-cube (PE↔PE) BW to 128 GB/s

Was 512 GB/s in the analytical viz MachineParams default. Bringing the
default down to 128 GB/s to match what the modelled physical link now
represents (parity with inter-cube D2D and topology.yaml).

Files touched (all three needed to keep defaults coherent):
  - model_config.py: MachineParams.bw_intra_gbs = 128.0 (was 512.0)
  - app.py: sidebar selectbox default index = 0 (128 GB/s) instead of 2 (512)
  - auto_hardware.py: _HW_KNOB_DEFAULTS + BALANCED + COARSE bw_intra_gbs
    baselines shifted so cost_score at defaults remains 6.0 and the
    sensitivity sweep starts from the new baseline.

Verified: 24 pytest tests pass.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/analytical_visualization/auto_hardware.py

@@ -38,7 +38,7 @@ _HW_KNOB_DEFAULTS = {
     "pe_hbm_gb":         6.0,
     "bw_hbm_gbs":        256.0,
     "peak_tflops_f16":   8.0,
-    "bw_intra_gbs":      512.0,
+    "bw_intra_gbs":      128.0,
     "bw_inter_gbs":      128.0,
     "bw_intersip_gbs":   50.0,
 }
@@ -47,7 +47,7 @@ _HW_VALUES_BALANCED = {
     "pe_hbm_gb":         [6.0, 12.0],
     "bw_hbm_gbs":        [256.0, 512.0],
     "peak_tflops_f16":   [8.0, 16.0],
-    "bw_intra_gbs":      [512.0, 1024.0],
+    "bw_intra_gbs":      [128.0, 256.0],
     "bw_inter_gbs":      [128.0, 256.0],
     "bw_intersip_gbs":   [50.0, 100.0],
 }
@@ -56,7 +56,7 @@ _HW_VALUES_COARSE = {
     "pe_hbm_gb":         [6.0, 12.0, 24.0],
     "bw_hbm_gbs":        [256.0, 512.0, 1024.0],
     "peak_tflops_f16":   [8.0, 16.0, 32.0],
-    "bw_intra_gbs":      [512.0, 1024.0, 2048.0],
+    "bw_intra_gbs":      [128.0, 256.0, 512.0],
     "bw_inter_gbs":      [128.0, 256.0, 512.0],
     "bw_intersip_gbs":   [50.0, 100.0, 200.0],
 }