fix(stop): the exit-4 refusal names where the holder may be (Issue #31, Mac review)

The refusal pointed at ~/.claude/sessions/ for every agent, whatever
CLAUDE_CONFIG_DIR said, and never mentioned a non-agent process naming the
uuid on its command line. The in-use CLI now prints, on stderr while the
conversation is in use, the adapter's in_use_hints: for every adapter
`ps -axww | grep <uuid>`, and for claude its real sessions/ dir first. stop
prints them under its refusal, and says "records preserved" instead of
"no state was modified": the gate runs after the kill chain, so the session
itself may already be down. SKILL.md's exit 4 row says the same; it is not
a code block, so no inventory hash moves.

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

.agents/skills/lib_py/agents/base.py

@@ -308,6 +308,11 @@ class BaseAgentAdapter:
         """True while a live process still references the conversation."""
         return conversation_in_use(uuid, [self.artifact_path(uuid, ctx)])
 
+    def in_use_hints(self, uuid: str, ctx: DiscoveryContext) -> list:
+        """Where to look for what holds the conversation, shown when a purge
+        is refused because it is in use."""
+        return [f"any process with it on its command line (an editor, a grep, ...): ps -axww | grep {uuid}"]
+
     def spawn_spec(self, binary: str, session_uuid: str = "", use_wrapper: bool = False) -> str:
         raise NotImplementedError