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/0074_design_prose.py

@@ -4,8 +4,7 @@ Revision ID: 0074
 Revises: 0073
 Create Date: 2026-07-31
 
-The operator's shape for #254: prose doesn't live as one-offs, it lives centrally
-on the system. Two fields rather than one per category:
+Prose doesn't live as one-offs; it lives centrally on the system. Two fields rather than one per category:
 
   design_systems.guidance   the narrative a token table cannot hold — aesthetic,
                             voice and tone, what is deliberately out of scope.
@@ -17,7 +16,7 @@ on the system. Two fields rather than one per category:
 
 Free-form rather than a column per category on purpose. A schema with `voice`,
 `aesthetic` and `scope` columns would bake one rulebook's table of contents into
-every install (rule #115), and the next install's design system would have three
+every install, and the next install's design system would have three
 empty columns and nowhere to put what it actually cares about.
 
 Both nullable: a design system with no prose at all is complete, not a draft.