Add TUI notification condition config (#17175)

Problem: TUI desktop notifications are hard-gated on terminal focus, so
terminal/IDE hosts that want in-focus notifications cannot opt in.

Solution: Add a flat `[tui] notification_condition` setting (`unfocused`
by default, `always` opt-in), carry grouped TUI notification settings
through runtime config, apply method + condition together in the TUI,
and regenerate the config schema.

codex-rs/core/config.schema.json

@@ -1108,6 +1108,24 @@
       },
       "type": "object"
     },
+    "NotificationCondition": {
+      "oneOf": [
+        {
+          "description": "Emit TUI notifications only while the terminal is unfocused.",
+          "enum": [
+            "unfocused"
+          ],
+          "type": "string"
+        },
+        {
+          "description": "Emit TUI notifications regardless of terminal focus.",
+          "enum": [
+            "always"
+          ],
+          "type": "string"
+        }
+      ]
+    },
     "NotificationMethod": {
       "enum": [
         "auto",
@@ -1812,6 +1830,15 @@
           "default": {},
           "description": "Startup tooltip availability NUX state persisted by the TUI."
         },
+        "notification_condition": {
+          "allOf": [
+            {
+              "$ref": "#/definitions/NotificationCondition"
+            }
+          ],
+          "default": "unfocused",
+          "description": "Controls whether TUI notifications are delivered only when the terminal is unfocused or regardless of focus. Defaults to `unfocused`."
+        },
         "notification_method": {
           "allOf": [
             {
@@ -1819,7 +1846,7 @@
             }
           ],
           "default": "auto",
-          "description": "Notification method to use for unfocused terminal notifications. Defaults to `auto`."
+          "description": "Notification method to use for terminal notifications. Defaults to `auto`."
         },
         "notifications": {
           "allOf": [
@@ -1828,7 +1855,7 @@
             }
           ],
           "default": true,
-          "description": "Enable desktop notifications from the TUI when the terminal is unfocused. Defaults to `true`."
+          "description": "Enable desktop notifications from the TUI. Defaults to `true`."
         },
         "show_tooltips": {
           "default": true,