Fix eterm tab closing and macOS menu integration

* Serialize tracked realloc and free bookkeeping to prevent cross-thread
    address reuse from corrupting the memory tracker during tab teardown.
  * Add concurrent allocation and terminal close/resize regression coverage.
  * Install a macOS-only File, Edit, and Window menu that mirrors eterm
    keybindings without binding Cmd+W.
  * Keep the native menu outside the splitter layout and document the canonical
    macOS build workflow.

.ecode/project_build.json

@@ -658,6 +658,12 @@
         "command": "${project_root}/bin/eepp-ui-markdownview-debug",
         "name": "eepp-ui-markdownview-debug",
         "working_dir": "${project_root}/bin/"
+      },
+      {
+        "args": "",
+        "command": "${project_root}/bin/eterm-debug",
+        "name": "eterm-debug",
+        "working_dir": "${project_root}/bin/"
       }
     ],
     "var": {