tui: queue follow-ups during manual /compact (#15259)

## Summary
- queue input after the user submits `/compact` until that manual
compact turn ends
- mirror the same behavior in the app-server TUI
- add regressions for input queued before compact starts and while it is
running

Co-authored-by: Codex <noreply@openai.com>

codex-rs/app-server-protocol/schema/json/v2/TurnStartedNotification.json

@@ -131,6 +131,28 @@
           ],
           "title": "ResponseTooManyFailedAttemptsCodexErrorInfo",
           "type": "object"
+        },
+        {
+          "additionalProperties": false,
+          "description": "Returned when `turn/start` or `turn/steer` is submitted while the current active turn cannot accept same-turn steering, for example `/review` or manual `/compact`.",
+          "properties": {
+            "activeTurnNotSteerable": {
+              "properties": {
+                "turnKind": {
+                  "$ref": "#/definitions/NonSteerableTurnKind"
+                }
+              },
+              "required": [
+                "turnKind"
+              ],
+              "type": "object"
+            }
+          },
+          "required": [
+            "activeTurnNotSteerable"
+          ],
+          "title": "ActiveTurnNotSteerableCodexErrorInfo",
+          "type": "object"
         }
       ]
     },
@@ -494,6 +516,13 @@
         }
       ]
     },
+    "NonSteerableTurnKind": {
+      "enum": [
+        "review",
+        "compact"
+      ],
+      "type": "string"
+    },
     "PatchApplyStatus": {
       "enum": [
         "inProgress",