fix: add writable global memory mount for main agent

Main group had no mount for the global memory directory
(/workspace/global), so it could only reach it through the read-only
project root. This meant the main agent couldn't write to global
memory despite groups/main/CLAUDE.md instructing it to do so.

Add a writable mount at /workspace/global for the isMain branch,
matching the read-only mount that non-main groups already have.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/container-runner.ts

@@ -104,6 +104,16 @@ function buildVolumeMounts(
       containerPath: '/workspace/group',
       readonly: false,
     });
+
+    // Global memory directory — writable for main so it can update shared context
+    const globalDir = path.join(GROUPS_DIR, 'global');
+    if (fs.existsSync(globalDir)) {
+      mounts.push({
+        hostPath: globalDir,
+        containerPath: '/workspace/global',
+        readonly: false,
+      });
+    }
   } else {
     // Other groups only get their own folder
     mounts.push({