docs(stop): the workflow and the state diagram say a purge removes the row (Issue #31)

SKILL.md lines 52 and 83 still said a purge leaves a `terminated` row. The
two blocks' inventory shas move with them (#42), and so does the
passthrough line of stop's heredoc SystemExit(1) (310 -> 327, after the
process gate). Line counts are unchanged, so no other block moves.

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

.agents/skills/multi-agent-mux-stop/SKILL.md

@@ -49,7 +49,7 @@ bash .agents/skills/multi-agent-mux-stop/scripts/stop_session.sh \
   --session "$SESSION_NAME" --agent "$AGENT" --reason api_error
 
 # 3. Stop gracefully + clean up on-disk conversation (DANGEROUS)
-#    — this prevents any future resume (status=terminated, resumable=false).
+#    — this prevents any future resume and removes the session's registry row (YAML+DB).
 bash .agents/skills/multi-agent-mux-stop/scripts/stop_session.sh \
   --session "$SESSION_NAME" --agent "$AGENT" --purge-conversation --yes
 ```
@@ -80,7 +80,7 @@ while its registry row survives.
 
 ```
 running ──(stop default / --reason)────────► stopped      (resumable:true, conv preserved)
-running ──(stop --purge-conversation --yes)► terminated   (resumable:false, conv deleted)
+running ──(stop --purge-conversation --yes)► row removed  (YAML+DB; conv deleted)
 stopped ──(stop default … again)───────────► stopped      (idempotent no-op)
 ```