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/0102_milestone_embeddings.py

@@ -1,4 +1,4 @@
-"""milestone_embeddings — a plan becomes findable by meaning (milestone 415)
+"""milestone_embeddings — a plan becomes findable by meaning
 
 Revision ID: 0102
 Revises: 0101
@@ -9,8 +9,8 @@ lives in — could not be found at all. So "is there already a plan for this?"
 had no tool, and a project whose roadmap was written as milestones had every
 later plan opened as a new milestone beside the one that already described it.
 
-The sibling of rule_embeddings (0089), for the reasons its model docstring and
-note 3163 give. The vectors are DERIVED: nothing is backfilled here, the startup
+The sibling of rule_embeddings (0089), for the reasons its model docstring
+gives. The vectors are DERIVED: nothing is backfilled here, the startup
 backfill writes them.
 """
 import sqlalchemy as sa