docs(6206): the remaining models, routes, mcp/tools/repos and config comments drop citations

A shipped tool docstring (mcp/tools/repos bind_repo) cited this instance's
"rule 1: dev is home"; it now says what a dev-branch project should do.
routes/knowledge, routes/tasks, routes/systems and models/retrieval_log state
the property each guards rather than the bug that once broke it.

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

src/scribe/models/system_usage.py

@@ -10,7 +10,7 @@ PULLED = "pulled"
 
 class SystemUsageEvent(Base, CreatedAtMixin):
     """One row per time a System's rulings were SHOWN to the agent because its
-    files were touched, or the System was PULLED in full (milestone 444).
+    files were touched, or the System was PULLED in full.
 
     The third of the usage tables, after `note_usage_events` and
     `rule_usage_events`, and separate from both for the reason the rule twin