Test exec catalog preservation across session and compaction changes (#60173)

## What changed

- Cover incremental exec tool settings and catalog changes across resume, fork, tool mode switches, and compaction.
- Verify that adopting background compaction preserves live exec declarations, tool metadata updates, and retained conversation order after a model catalog refresh.
- Include an `exec` namespace in the top-level tool catalog ordering and snapshot round-trip test.

GitOrigin-RevId: 3df603b98a006abb55a5095b299080f036576242

codex-rs/core/src/context/world_state/top_level_tools_tests.rs

@@ -267,6 +267,7 @@ fn initial_catalog_preserves_order_and_unchanged_catalog_emits_nothing() {
     let definitions = vec![
         namespace("zebra", vec![declaration("lookup")]),
         namespace("alpha", vec![declaration("lookup")]),
+        namespace("exec", vec![declaration("lookup")]),
     ];
     let state = TopLevelToolsState::new(
         /*messages*/ Default::default(),
@@ -293,7 +294,14 @@ fn initial_catalog_preserves_order_and_unchanged_catalog_emits_nothing() {
             .keys()
             .map(String::as_str)
             .collect::<Vec<_>>(),
-        vec!["alpha", "alpha.lookup", "zebra", "zebra.lookup"]
+        vec![
+            "alpha",
+            "alpha.lookup",
+            "exec",
+            "exec.lookup",
+            "zebra",
+            "zebra.lookup"
+        ]
     );
     let snapshot: TopLevelToolsSnapshot = serde_json::from_value(saved).unwrap();
     let (unchanged_snapshot, updates) = state.render_diff(PreviousSectionState::Known(&snapshot));