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/derive-protected-experts.py

@@ -2,7 +2,7 @@
 """derive-protected-experts.py — rewrite the recipe's protected-expert section
 from a calibration recording. RUNS ON DANKSERVER (venv: numpy).
 
-The law (docs/MOE-W4.md "Protected experts", restated in the recipe):
+The selection rule (docs/MOE-W4.md "Protected experts", restated in the recipe):
 an expert whose share of its layer's down-input energy is at least 3% AND
 at least three times its share of the routing is kept bf16; the count must
 be EVEN on each rank's half of the layer (the four-bit GEMM takes the rest