[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/core/src/memory_usage.rs

@@ -5,7 +5,6 @@ use crate::tools::handlers::unified_exec::ExecCommandArgs;
 use codex_memories_read::usage::MEMORIES_USAGE_METRIC;
 use codex_memories_read::usage::memories_usage_kinds_from_command;
 use codex_protocol::models::ShellCommandToolCallParams;
-use codex_protocol::models::ShellToolCallParams;
 use std::path::PathBuf;
 
 pub(crate) async fn emit_metric_for_tool_read(invocation: &ToolInvocation, success: bool) {
@@ -41,14 +40,6 @@ fn shell_command_for_invocation(invocation: &ToolInvocation) -> Option<(Vec<Stri
         invocation.tool_name.namespace.as_deref(),
         invocation.tool_name.name.as_str(),
     ) {
-        (None, "shell") => serde_json::from_str::<ShellToolCallParams>(arguments)
-            .ok()
-            .map(|params| {
-                (
-                    params.command,
-                    invocation.turn.resolve_path(params.workdir).to_path_buf(),
-                )
-            }),
         (None, "shell_command") => serde_json::from_str::<ShellCommandToolCallParams>(arguments)
             .ok()
             .map(|params| {