chore(stop,resume): drop what Issue #63 left unused (Issue #63)

- workspace_uuid.py: the unused sys import.
- stop_session.sh: the orphan CAPTURE_ID and the blank padding that kept
  later line numbers; the inventory pins follow the move instead.
- lib.sh: capture_conversation_id, which nothing calls any more.
- resume SKILL.md: the flow names the session-id decision (session_ids.py),
  not resolve_session_id.sh.

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

tests/data/skill_code_blocks.json

@@ -433,7 +433,7 @@
    "class": "c",
    "kind": "diagram",
    "evidence": [
-    "multi-agent-mux-stop/scripts/stop_session.sh:184-198"
+    "multi-agent-mux-stop/scripts/stop_session.sh:183-197"
    ],
    "mismatch": null,
    "note": "state machine"
@@ -503,9 +503,9 @@
    "base_sha": "a7ed3e902cae",
    "class": "a",
    "evidence": [
-    "multi-agent-mux-stop/scripts/stop_session.sh:99",
-    "multi-agent-mux-stop/scripts/stop_session.sh:140-143",
-    "multi-agent-mux-stop/scripts/stop_session.sh:184-188"
+    "multi-agent-mux-stop/scripts/stop_session.sh:98",
+    "multi-agent-mux-stop/scripts/stop_session.sh:139-142",
+    "multi-agent-mux-stop/scripts/stop_session.sh:183-187"
    ],
    "mismatch": [
     "T1: the doc offered --force-no-yaml, which no script accepts"
@@ -599,7 +599,7 @@
     "other"
    ],
    "passthrough": {
-    "1": "multi-agent-mux-stop/scripts/stop_session.sh:327"
+    "1": "multi-agent-mux-stop/scripts/stop_session.sh:322"
    }
   },
   "multi-agent-mux-create/scripts/create_session.sh": {