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/serve-frank-dragoon.sh

@@ -72,9 +72,10 @@ set +a
 require_image "$FRANK_DRAGOON_IMAGE" \
     "pull it: podman pull docker://$FRANK_DRAGOON_IMAGE" || exit 1
 
-# Size-exact gates on all three payload files: a truncated curl exits 0 on
-# some failures and a partial .hgn loads far enough to look alive, so the
-# byte counts from the Hub tree API are the contract (fleet fetch law).
+# Size-exact gates on all three payload files: a truncated download can
+# exit 0, and a partial .hgn loads far enough to look alive, so existence
+# proves nothing. The byte count published by the Hub tree API is the
+# contract: any other size is a different (broken) artifact.
 require_bytes "$FRANK_DRAGOON_MODEL_DIR/$FRANK_DRAGOON_CHECKPOINT" \
     checkpoint "$FRANK_DRAGOON_CHECKPOINT_BYTES" \
     "fetch it: bash scripts/download-frank-dragoon-flashnext.sh" || exit 1