Add transcript search and per-activity detail controls (#46734)

## What changed

- Add incremental, case-insensitive literal search across transcript details, loading older history as needed. Use `F3` to start Find, or `/` in the transcript pager, and navigate matches in either direction. Closing Find restores the previous presentation and reading position.
- Add clickable activity detail controls and `F4` keyboard focus for inspecting individual activity groups in the owned transcript. Preserve expansion state as live activity becomes history.
- Expose configurable `global.find_transcript`, `global.focus_activity`, and `pager.find` bindings under `tui.keymap`. Let new defaults yield to existing custom bindings and show available completions for pending chords.

## Testing

Add regression coverage for Unicode matching, bounded scanning, paginated and changing history, selection during search, composer input isolation, activity controls, and custom shortcut conflicts.

GitOrigin-RevId: 5bcbcdfbca7c5c296c635ec9b079ccd7a908e336

codex-rs/config/src/tui_keymap.rs

@@ -96,6 +96,10 @@ pub struct TuiGlobalKeymap {
     pub open_agents: Option<KeybindingsSpec>,
     /// Open the transcript overlay.
     pub open_transcript: Option<KeybindingsSpec>,
+    /// Find text in the full transcript.
+    pub find_transcript: Option<KeybindingsSpec>,
+    /// Focus activity groups in the owned transcript to inspect their details.
+    pub focus_activity: Option<KeybindingsSpec>,
     /// Open the external editor for the current draft.
     pub open_external_editor: Option<KeybindingsSpec>,
     /// Copy the last agent response to the clipboard.
@@ -401,6 +405,8 @@ pub struct TuiPagerKeymap {
     pub close: Option<KeybindingsSpec>,
     /// Close the transcript overlay via its dedicated toggle key.
     pub close_transcript: Option<KeybindingsSpec>,
+    /// Find text in a transcript pager.
+    pub find: Option<KeybindingsSpec>,
 }
 
 /// List selection context keybindings for popup-style selectable lists.
@@ -769,6 +775,48 @@ mod tests {
         assert!(keymap.global.open_transcript.is_some());
     }
 
+    #[test]
+    fn transcript_find_accepts_custom_chords_and_can_be_disabled() {
+        for (bindings, expected) in [
+            (
+                "'ctrl-x f'",
+                KeybindingsSpec::One(KeybindingSpec("ctrl-x f".to_owned())),
+            ),
+            ("[]", KeybindingsSpec::Many(Vec::new())),
+        ] {
+            for (context, action) in [("pager", "find"), ("global", "find_transcript")] {
+                let keymap: TuiKeymap =
+                    toml::from_str(&format!("[{context}]\n{action} = {bindings}\n"))
+                        .expect("Find binding");
+                let mut expected_keymap = TuiKeymap::default();
+                if context == "pager" {
+                    expected_keymap.pager.find = Some(expected.clone());
+                } else {
+                    expected_keymap.global.find_transcript = Some(expected.clone());
+                }
+                assert_eq!(keymap, expected_keymap);
+            }
+        }
+    }
+
+    #[test]
+    fn activity_focus_accepts_custom_chords_and_can_be_disabled() {
+        for (bindings, expected) in [
+            (
+                "'ctrl-x t'",
+                KeybindingsSpec::One(KeybindingSpec("ctrl-x t".to_owned())),
+            ),
+            ("[]", KeybindingsSpec::Many(Vec::new())),
+        ] {
+            let keymap: TuiKeymap =
+                toml::from_str(&format!("[global]\nfocus_activity = {bindings}\n"))
+                    .expect("activity focus binding");
+            let mut expected_keymap = TuiKeymap::default();
+            expected_keymap.global.focus_activity = Some(expected);
+            assert_eq!(keymap, expected_keymap);
+        }
+    }
+
     #[test]
     fn minus_bindings_under_global_context_are_accepted() {
         for (spec, expected) in [