make 5.3-codex visible in cli for api users (#12808)

5.3-codex released in api, mark it visible for API users via bundled
`models.json`.

codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__model_selection_popup.snap

@@ -5,12 +5,13 @@ expression: popup
   Select Model and Effort
   Access legacy models by running codex -m <model_name> or in your config.toml
 
-› 1. gpt-5.2-codex (default)  Frontier agentic coding model.
-  2. gpt-5.1-codex-max        Codex-optimized flagship for deep and fast
+› 1. gpt-5.3-codex (default)  Latest frontier agentic coding model.
+  2. gpt-5.2-codex            Frontier agentic coding model.
+  3. gpt-5.1-codex-max        Codex-optimized flagship for deep and fast
                               reasoning.
-  3. gpt-5.2                  Latest frontier model with improvements across
+  4. gpt-5.2                  Latest frontier model with improvements across
                               knowledge, reasoning and coding
-  4. gpt-5.1-codex-mini       Optimized for codex. Cheaper, faster, but less
+  5. gpt-5.1-codex-mini       Optimized for codex. Cheaper, faster, but less
                               capable.
 
   Press enter to select reasoning effort, or esc to dismiss.