Add computer_use feature requirement key (#19071)

## Summary
- add the `computer_use` requirements-only feature key
- include it in generated config schema output
- cover the new key in feature metadata tests

## Testing
- `cargo test -p codex-features`
- `just write-config-schema`
- `just fmt`
- `just fix -p codex-features`

cc @xl-openai

---------

Co-authored-by: Dylan Hurd <dylan.hurd@openai.com>

codex-rs/core/config.schema.json

@@ -378,6 +378,9 @@
             "collaboration_modes": {
               "type": "boolean"
             },
+            "computer_use": {
+              "type": "boolean"
+            },
             "connectors": {
               "type": "boolean"
             },
@@ -2532,6 +2535,9 @@
         "collaboration_modes": {
           "type": "boolean"
         },
+        "computer_use": {
+          "type": "boolean"
+        },
         "connectors": {
           "type": "boolean"
         },