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/0066_milestone_body.py

@@ -4,7 +4,7 @@ Revision ID: 0066
 Revises: 0065
 Create Date: 2026-06-14
 
-T3 of plan #819. The milestone becomes the plan container: its `body` holds
+The milestone becomes the plan container: its `body` holds
 the design/intent/purpose (markdown), `description` stays the one-liner, and
 individual steps live as first-class child tasks (milestone_id) instead of
 checkboxes crammed into a kind=plan task body. start_planning is reworked to