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/0078_forge_connections.py

@@ -1,4 +1,4 @@
-"""Forge connections move to the user level (#2778)
+"""Forge connections move to the user level
 
 Revision ID: 0078
 Revises: 0077
@@ -12,7 +12,7 @@ keyring, with an optional per-project pin (projects.forge_connection_id).
 
 The data move carries the existing admin config into a connection row for the
 first admin user (host parsed from the base URL), then deletes the old
-setting keys outright — no legacy dual-read (rule #22). The env-var channel
+setting keys outright — no legacy dual-read. The env-var channel
 (FORGE_KIND/FORGE_BASE_URL/FORGE_TOKEN) is untouched by this migration; it
 survives as an implicit keyring entry for admin users only.
 """