docs(6205): the remaining services files state the reason, not the instance that taught it

The 1-2 hit tail: access, background, backup, backup_job, canonical_systems,
design_stylesheet, forge_connections, moment_actions, notes, notifications,
placement, planning, platforms, projects, record_batch, recurrence,
report_check, retrieval_review, rule_scope, rule_versions, scheduler,
shape_check, supersession, system_rulings, system_usage, text, trash,
verification, version_pinning.

Also corrected while reading:
- backup.py said restore step 16 fills the System map; step 15 does.
- version_pinning.py pointed at a design doc that is not in the repo.

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

src/scribe/services/platforms.py

@@ -1,5 +1,5 @@
 """Platforms — what a project is built on or ships as, and which projects are
-which (milestone 463 step 2).
+which.
 
 Membership is what makes "is this idea in family for that project?" a lookup
 rather than a judgment: a family idea is for some platforms, and it reaches
@@ -266,7 +266,7 @@ async def set_project_platforms(
     user_id: int, project_id: int, updates: dict[str, str | None],
 ) -> list[dict]:
     """Apply a person's answers about a project's platforms. Write-gated on
-    the project (rule 78). Platforms not named are left exactly as they are.
+    the project. Platforms not named are left exactly as they are.
 
     Raises ValueError, naming the problem, on a malformed update, an unknown
     slug, or no write access — before anything is written, so the update