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>

tests/data/skill_code_blocks.json

@@ -413,7 +413,7 @@
    "start": 42,
    "end": 55,
    "lang": "bash",
-   "sha": "27ebf150b92a",
+   "sha": "301c347ff881",
    "class": "c",
    "kind": "invocation",
    "evidence": [
@@ -429,7 +429,7 @@
    "start": 81,
    "end": 85,
    "lang": "-",
-   "sha": "a2b56ac238ae",
+   "sha": "a973676cb2d1",
    "class": "c",
    "kind": "diagram",
    "evidence": [
@@ -599,7 +599,7 @@
     "other"
    ],
    "passthrough": {
-    "1": "multi-agent-mux-stop/scripts/stop_session.sh:310"
+    "1": "multi-agent-mux-stop/scripts/stop_session.sh:327"
    }
   },
   "multi-agent-mux-create/scripts/create_session.sh": {