docs(6207): migrations 0101, 0105, 0106, 0108, 0120, 0121 drop citations and the operator quote

0121 keeps the ARM_BORN date beside the constant it justifies.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

alembic/versions/0101_drop_rulebook_subscriptions.py

@@ -4,12 +4,12 @@ Revision ID: 0101
 Revises: 0100
 Create Date: 2026-09-15
 
-Milestone 414. A rule lives in a rulebook topic, where it is GLOBAL, or on one
-project, and retrieval reads that home directly (step 1). Subscriptions were
-the last thing that pretended a rulebook reached some projects and not others,
-and after milestone 394 they changed nothing a session received — only what a
-project's rule LISTING showed. Operator, 2026-09-15: "we have global and
-project scoped rules, we don't need the subscriptions now."
+A rule lives in a rulebook topic, where it is GLOBAL, or on one project, and
+retrieval reads that home directly. Subscriptions were the last thing that
+pretended a rulebook reached some projects and not others, and with no
+always-on tier they changed nothing a session received — only what a
+project's rule LISTING showed. Global and project-scoped rules cover what
+subscriptions were for.
 
 WHAT GOES
 
@@ -19,8 +19,8 @@ WHAT GOES
     there is nothing to mute; a project that departs from a global rule writes
     a project rule with an ``overrides`` relation, which says why.
   - The ``subscribe_rulebooks`` key inside ``projects.inception.choices``, and
-    the ``exclude_always_on_rulebooks`` key milestone 394 left behind in the
-    same place. Both describe decisions that can no longer be made; a stored
+    the ``exclude_always_on_rulebooks`` key the retired always-on tier left
+    in the same place. Both describe decisions that can no longer be made; a stored
     record carrying them would be read back as a choice the product offers.
 
 IRREVERSIBLE, AND THE DOWNGRADE SAYS SO