Fill the single missing section in three scripts that had everything else

AI/ai_token_sync.sh

@@ -30,6 +30,31 @@
 # fetches its own data controls its own freshness rather than depending on the partner's cron.
 #
 # ==============================================================================================
+# DESIGN PRINCIPLES
+# ==============================================================================================
+#
+# A missing file means unknown, never zero.
+#   The whole point of the tab reporting "not collected here" is that it is a different claim
+#   from "this partner spent nothing". If a partner is dark, unreachable or has never run a turn,
+#   there is simply no cache file, and the reader is expected to say so rather than render a 0
+#   that looks like a measurement.
+#
+# The reader pulls; nobody pushes.
+#   conf_sync.sh pushes as well, because a partner that cannot reach us still needs our
+#   credentials. Nothing here is needed by anyone else, so a host that wants fleet totals fetches
+#   them and owns its own freshness instead of depending on someone else's cron having run.
+#
+# RAM, not flash.
+#   The cache lands in tmpfs. It is a copy of a file that already exists on the partner and is
+#   rebuilt on the next pass, so writing it to flash would cost wear for something that is never
+#   worth surviving a reboot.
+#
+# Same shape as conf_sync.sh, deliberately.
+#   Resolve over Tailscale, scp one small file into a tmpfs cache, let a missing file mean
+#   unknown. A second transport pattern for a second small file would be a second set of
+#   failure modes to learn.
+#
+# ==============================================================================================
 # OPERATIONAL SAFEGUARDS
 # ==============================================================================================
 #