refact(comments): state the mechanism, not the incident

Every comment that invoked a 'law' (50 word-boundary sites across 28
tracked files) now states what is going on and why, in terms that
transfer to any project: gate twins drift until one side greenlights
what the other refuses; a tag re-points while a digest pins; a
restrictive engine behavior belongs to the runtime that imposed it and
must be re-tested, not inherited; a speculative head is tensors in the
file, not a flag; snapshot links dangle where the container resolves
them; exit 0 is a clean stop to systemd, so a self-exiting daemon on
on-failure goes dark reporting success. Event narratives and dates are
gone from these comments; the mechanics carry the argument.

Behavior-identical: bash -n, py_compile, yaml parse, full bats suite
408/408 green. One symbol rename rides along (stack script local
scale_law -> scale_contract, with its log text).

scripts/stack-qwen38-official-fp8.py

@@ -293,12 +293,12 @@ def main():
     ddt, dsh = meta[f"{pre0}.mlp.experts.0.down_proj.weight"][3:5]
     gsd, gssh = meta[f"{pre0}.mlp.experts.0.gate_proj.weight_scale_inv"][3:5]
     dsd, dssh = meta[f"{pre0}.mlp.experts.0.down_proj.weight_scale_inv"][3:5]
-    scale_law = (gdt == F8 and ddt == F8 and gsd == BF16 and dsd == BF16
+    scale_contract = (gdt == F8 and ddt == F8 and gsd == BF16 and dsd == BF16
                  and list(gssh) == [(gsh[0] + 127) // 128, (gsh[1] + 127) // 128]
                  and list(dssh) == [(dsh[0] + 127) // 128, (dsh[1] + 127) // 128])
-    if not scale_law:
+    if not scale_contract:
         log(f"ERROR: unexpected expert shapes: gate {gdt}{gsh} scale {gsd}{gssh} "
-            f"down {ddt}{dsh} scale {dsd}{dssh} (scale law 128x128)")
+            f"down {ddt}{dsh} scale {dsd}{dssh} (fp8 block scales cover 128x128 tiles)")
         return 2
     shapes = {"ffn2_h": (gsh[0] * 2, gsh[1]), "ffn": (dsh[1],),
               "gs": tuple(gssh), "ds": tuple(dssh)}