fix(hooks): remove Stop hook that caused 30s timeouts (gt-quoj)

The Stop hook with `gt costs record` was causing 30-second timeouts
on every session stop due to beads socket connection issues. Since
cost tracking is disabled anyway (Claude Code doesn't expose session
costs), this hook provided no value.

Changes:
- Remove Stop hook from settings-autonomous.json and settings-interactive.json
- Remove Stop hook validation from claude_settings_check.go
- Update tests to not expect Stop hook

The cost tracking infrastructure remains in costs.go for future use
when Claude Code exposes session costs via API or environment variable.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/claude/config/settings-interactive.json

@@ -65,17 +65,6 @@
           }
         ]
       }
-    ],
-    "Stop": [
-      {
-        "matcher": "",
-        "hooks": [
-          {
-            "type": "command",
-            "command": "export PATH=\"$HOME/go/bin:$HOME/bin:$PATH\" && gt costs record"
-          }
-        ]
-      }
     ]
   }
 }