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).

tests/llm_gates.bats

@@ -1,11 +1,11 @@
 #!/usr/bin/env bats
 # Seam: the shared artifact gates every LLM endpoint runs before it starts.
 #
-# The fleet law these encode: a serve script and the deployer must refuse the
-# SAME missing/truncated artifact, and they must refuse it the same way,
-# because the 2026-10-01 crash-loop was exactly those two gates disagreeing
-# mid-cutover (green deploy, red unit). The library is the one place the
-# refusal lives; both callers source it.
+# The rule these encode: a serve script and the deployer must refuse the
+# SAME missing/truncated artifact, and they must refuse it the same way.
+# Two hand-written copies of the same gates drift apart until a deploy
+# passes what the unit would refuse; the library is the one place the
+# refusal lives, and both callers source it.
 #
 # Everything here is observable: arguments in, exit status and stderr out.
 # Nothing inspects the library's internals.