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).

shared/services.yml

@@ -93,8 +93,8 @@ services:
     kind: quadlet
     unit_dir: dankclaw/searxng/quadlet
     units: [searxng-valkey]
-    # The app-level law, not a network one: deploy_searxng_valkey restarts
-    # SearXNG after its cache, so the cache's files select both.
+    # An app-level dependency, not a network one: the deploy handler
+    # restarts SearXNG after its cache, so the cache's files select both.
     dependents: [searxng]
     tests: [tests/searxng_quadlet.bats]
     probe: 127.0.0.1:6379