chore: upgrade to Rust 1.92.0 (#8860)

**Summary**
- Upgrade Rust toolchain used by CI to 1.92.0.
- Address new clippy `derivable_impls` warnings by deriving `Default`
for enums across protocol, core, backend openapi models, and
windows-sandbox setup.
- Tidy up related test/config behavior (originator header handling, env
override cleanup) and remove a now-unused assignment in TUI/TUI2 render
layout.

**Testing**
- `just fmt`
- `just fix -p codex-tui`
- `just fix -p codex-tui2`
- `just fix -p codex-windows-sandbox`
- `cargo test -p codex-tui`
- `cargo test -p codex-tui2`
- `cargo test -p codex-windows-sandbox`
- `cargo test -p codex-core --test all`
- `cargo test -p codex-app-server --test all`
- `cargo test -p codex-mcp-server --test all`
- `cargo test --all-features`

codex-rs/core/src/config/types.rs

@@ -423,10 +423,11 @@ impl Default for Notifications {
 /// Terminals generally encode both mouse wheels and trackpads as the same "scroll up/down" mouse
 /// button events, without a magnitude. This setting controls whether Codex uses a heuristic to
 /// infer wheel vs trackpad per stream, or forces a specific behavior.
-#[derive(Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, JsonSchema)]
+#[derive(Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, JsonSchema, Default)]
 #[serde(rename_all = "snake_case")]
 pub enum ScrollInputMode {
     /// Infer wheel vs trackpad behavior per scroll stream.
+    #[default]
     Auto,
     /// Always treat scroll events as mouse-wheel input (fixed lines per tick).
     Wheel,
@@ -434,12 +435,6 @@ pub enum ScrollInputMode {
     Trackpad,
 }
 
-impl Default for ScrollInputMode {
-    fn default() -> Self {
-        Self::Auto
-    }
-}
-
 /// Collection of settings that are specific to the TUI.
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, JsonSchema)]
 #[schemars(deny_unknown_fields)]