Open new sessions directly from the command center (#45255)

## What changed

- Replace the inline task composer with a session list: `n` opens a blank session in the selected checkout without sending an initial turn or interrupting running agents.
- Use single-letter action shortcuts and `Enter` to open a session. `Esc` cancels search or rename without closing the list; `Ctrl+C` quits from the list.
- Load destination settings for new sessions while carrying over explicit permission choices. Retain blank sessions and their drafts across navigation until the first turn.

## Testing

Update tests and snapshots for command center navigation, shortcuts, blank draft restoration, destination defaults, permission carryover, and directory trust.

GitOrigin-RevId: bddd04fdbe6ac2f5b7bd70293fd04f673b97ba02

codex-rs/core/config.schema.json

@@ -4429,7 +4429,7 @@
               "$ref": "#/definitions/KeybindingsSpec"
             }
           ],
-          "description": "Start composing a new agent task."
+          "description": "Open a new session in the selected checkout."
         },
         "rename": {
           "allOf": [