[codex] Remove unused legacy shell tools (#22246)

## Why

Recent session history showed no active use of the raw `shell`,
`local_shell`, or `container.exec` execution surfaces. Keeping those
handlers/specs wired into core leaves duplicate shell execution paths
alongside the supported `shell_command` and unified exec tools.

## What changed

- Removed the raw `shell` handler/spec and its `ShellToolCallParams`
protocol helper.
- Removed the legacy `local_shell` and `container.exec` handler/spec
plumbing while preserving persisted-history compatibility for old
response items.
- Normalized model/config `default` and `local` shell selections to
`shell_command`.
- Pruned tests that exercised removed raw-shell/local-shell/apply-patch
variants and kept coverage on `shell_command`, unified exec, and
freeform `apply_patch`.

## Verification

- `git diff --check`
- `cargo test -p codex-protocol`
- `cargo test -p codex-tools`
- `cargo test -p codex-core tools::handlers::shell`
- `cargo test -p codex-core tools::spec`
- `cargo test -p codex-core tools::router`
- `cargo test -p codex-core
active_call_preserves_triggering_command_context`
- `cargo test -p codex-core guardian_tests`
- `cargo test -p codex-core --test all shell_serialization`
- `cargo test -p codex-core --test all apply_patch_cli`
- `cargo test -p codex-core --test all shell_command_`
- `cargo test -p codex-core --test all local_shell`
- `cargo test -p codex-core --test all otel::`
- `cargo test -p codex-core --test all hooks::`
- `just fix -p codex-core`
- `just fix -p codex-tools`

codex-rs/tools/src/code_mode.rs

@@ -136,8 +136,7 @@ fn code_mode_tool_definitions_for_spec(spec: &ToolSpec) -> Vec<CodeModeToolDefin
                 }
             })
             .collect(),
-        ToolSpec::LocalShell {}
-        | ToolSpec::ImageGeneration { .. }
+        ToolSpec::ImageGeneration { .. }
         | ToolSpec::ToolSearch { .. }
         | ToolSpec::WebSearch { .. } => Vec::new(),
     }

codex-rs/tools/src/function_call_error.rs

@@ -5,8 +5,6 @@ use thiserror::Error;
 pub enum FunctionCallError {
     #[error("{0}")]
     RespondToModel(String),
-    #[error("LocalShellCall without call_id or id")]
-    MissingLocalShellCallId,
     #[error("Fatal error: {0}")]
     Fatal(String),
 }

codex-rs/tools/src/tool_config.rs

@@ -203,6 +203,9 @@ impl ToolsConfig {
             ConfigShellToolType::UnifiedExec if !unified_exec_enabled => {
                 ConfigShellToolType::ShellCommand
             }
+            ConfigShellToolType::Default | ConfigShellToolType::Local => {
+                ConfigShellToolType::ShellCommand
+            }
             other => other,
         };
         let shell_type = if !features.enabled(Feature::ShellTool) {

codex-rs/tools/src/tool_payload.rs

@@ -1,7 +1,6 @@
 use std::borrow::Cow;
 
 use codex_protocol::models::SearchToolCallParams;
-use codex_protocol::models::ShellToolCallParams;
 
 /// Canonical payload shapes accepted by model-visible tool runtimes.
 #[derive(Clone, Debug)]
@@ -9,7 +8,6 @@ pub enum ToolPayload {
     Function { arguments: String },
     ToolSearch { arguments: SearchToolCallParams },
     Custom { input: String },
-    LocalShell { params: ShellToolCallParams },
 }
 
 impl ToolPayload {
@@ -18,7 +16,6 @@ impl ToolPayload {
             ToolPayload::Function { arguments } => Cow::Borrowed(arguments),
             ToolPayload::ToolSearch { arguments } => Cow::Owned(arguments.query.clone()),
             ToolPayload::Custom { input } => Cow::Borrowed(input),
-            ToolPayload::LocalShell { params } => Cow::Owned(params.command.join(" ")),
         }
     }
 }

codex-rs/tools/src/tool_spec.rs

@@ -25,8 +25,6 @@ pub enum ToolSpec {
         description: String,
         parameters: JsonSchema,
     },
-    #[serde(rename = "local_shell")]
-    LocalShell {},
     #[serde(rename = "image_generation")]
     ImageGeneration { output_format: String },
     // TODO: Understand why we get an error on web_search although the API docs
@@ -58,7 +56,6 @@ impl ToolSpec {
             ToolSpec::Function(tool) => tool.name.as_str(),
             ToolSpec::Namespace(namespace) => namespace.name.as_str(),
             ToolSpec::ToolSearch { .. } => "tool_search",
-            ToolSpec::LocalShell {} => "local_shell",
             ToolSpec::ImageGeneration { .. } => "image_generation",
             ToolSpec::WebSearch { .. } => "web_search",
             ToolSpec::Freeform(tool) => tool.name.as_str(),

codex-rs/tools/src/tool_spec_tests.rs

@@ -57,7 +57,6 @@ fn tool_spec_name_covers_all_variants() {
         .name(),
         "tool_search"
     );
-    assert_eq!(ToolSpec::LocalShell {}.name(), "local_shell");
     assert_eq!(
         ToolSpec::ImageGeneration {
             output_format: "png".to_string(),