docs(6207): the remaining migrations state their rationale in terms of the data

Record, milestone, phase and plan citations go from every migration header;
the "end before start" fix (0043) and the suppressed-count column (0095)
state the condition they prevent rather than the incident. 0053 and 0055
pointed at design specs under docs/superpowers that are not in the repo;
those pointers are removed.

Kept: alembic's generated "Create Date:" headers (template metadata, not
rationale), 0121's ARM_BORN justification beside the constant, and 0051's
illustrative "update task 42" format example.

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

alembic/versions/0098_rule_kind.py

@@ -1,4 +1,4 @@
-"""rules gain a `kind` — a preference is a rule that does not bind (#3849)
+"""rules gain a `kind` — a preference is a rule that does not bind
 
 Revision ID: 0098
 Revises: 0097
@@ -37,7 +37,7 @@ install upgrades and every existing row keeps the force it had. That is the
 same reasoning 0088 used for `tier`, and it is the reason both are safe to
 apply without reading the data first.
 
-The CHECK is created with the column (rule 36: there is no prior constraint,
+The CHECK is created with the column (there is no prior constraint,
 so the pair is created together — a value added to it LATER does DROP + ADD
 in one migration).