feat: pass helper executable paths via Arg0DispatchPaths (#12719)

## Why

`codex-rs/core/src/tools/runtimes/shell/unix_escalation.rs` previously
located `codex-execve-wrapper` by scanning `PATH` and sibling
directories. That lookup is brittle and can select the wrong binary when
the runtime environment differs from startup assumptions.

We already pass `codex-linux-sandbox` from `codex-arg0`;
`codex-execve-wrapper` should use the same startup-driven path plumbing.

## What changed

- Introduced `Arg0DispatchPaths` in `codex-arg0` to carry both helper
executable paths:
  - `codex_linux_sandbox_exe`
  - `main_execve_wrapper_exe`
- Updated `arg0_dispatch_or_else()` to pass `Arg0DispatchPaths` to
top-level binaries and preserve helper paths created in
`prepend_path_entry_for_codex_aliases()`.
- Threaded `Arg0DispatchPaths` through entrypoints in `cli`, `exec`,
`tui`, `app-server`, and `mcp-server`.
- Added `main_execve_wrapper_exe` to core configuration plumbing
(`Config`, `ConfigOverrides`, and `SessionServices`).
- Updated zsh-fork shell escalation to consume the configured
`main_execve_wrapper_exe` and removed path-sniffing fallback logic.
- Updated app-server config reload paths so reloaded configs keep the
same startup-provided helper executable paths.

## References

- [`Arg0DispatchPaths`
definition](e355b43d5c/codex-rs/arg0/src/lib.rs (L20-L24))
- [`arg0_dispatch_or_else()` forwarding both
paths](e355b43d5c/codex-rs/arg0/src/lib.rs (L145-L176))
- [zsh-fork escalation using configured wrapper
path](e355b43d5c/codex-rs/core/src/tools/runtimes/shell/unix_escalation.rs (L109-L150))

## Testing

- `cargo check -p codex-arg0 -p codex-core -p codex-exec -p codex-tui -p
codex-mcp-server -p codex-app-server`
- `cargo test -p codex-arg0`
- `cargo test -p codex-core tools::runtimes::shell::unix_escalation:: --
--nocapture`

codex-rs/app-server/src/codex_message_processor.rs

@@ -168,6 +168,7 @@ use codex_app_server_protocol::WindowsSandboxSetupMode;
 use codex_app_server_protocol::WindowsSandboxSetupStartParams;
 use codex_app_server_protocol::WindowsSandboxSetupStartResponse;
 use codex_app_server_protocol::build_turns_from_rollout_items;
+use codex_arg0::Arg0DispatchPaths;
 use codex_backend_client::Client as BackendClient;
 use codex_chatgpt::connectors;
 use codex_cloud_requirements::cloud_requirements_loader;
@@ -338,7 +339,7 @@ pub(crate) struct CodexMessageProcessor {
     auth_manager: Arc<AuthManager>,
     thread_manager: Arc<ThreadManager>,
     outgoing: Arc<OutgoingMessageSender>,
-    codex_linux_sandbox_exe: Option<PathBuf>,
+    arg0_paths: Arg0DispatchPaths,
     config: Arc<Config>,
     single_client_mode: bool,
     cli_overrides: Vec<(String, TomlValue)>,
@@ -362,7 +363,7 @@ pub(crate) struct CodexMessageProcessorArgs {
     pub(crate) auth_manager: Arc<AuthManager>,
     pub(crate) thread_manager: Arc<ThreadManager>,
     pub(crate) outgoing: Arc<OutgoingMessageSender>,
-    pub(crate) codex_linux_sandbox_exe: Option<PathBuf>,
+    pub(crate) arg0_paths: Arg0DispatchPaths,
     pub(crate) config: Arc<Config>,
     pub(crate) cli_overrides: Vec<(String, TomlValue)>,
     pub(crate) cloud_requirements: Arc<RwLock<CloudRequirementsLoader>>,
@@ -399,7 +400,7 @@ impl CodexMessageProcessor {
             auth_manager,
             thread_manager,
             outgoing,
-            codex_linux_sandbox_exe,
+            arg0_paths,
             config,
             cli_overrides,
             cloud_requirements,
@@ -410,7 +411,7 @@ impl CodexMessageProcessor {
             auth_manager,
             thread_manager,
             outgoing: outgoing.clone(),
-            codex_linux_sandbox_exe,
+            arg0_paths,
             config,
             single_client_mode,
             cli_overrides,
@@ -426,7 +427,7 @@ impl CodexMessageProcessor {
 
     async fn load_latest_config(&self) -> Result<Config, JSONRPCErrorError> {
         let cloud_requirements = self.current_cloud_requirements();
-        codex_core::config::ConfigBuilder::default()
+        let mut config = codex_core::config::ConfigBuilder::default()
             .cli_overrides(self.cli_overrides.clone())
             .cloud_requirements(cloud_requirements)
             .build()
@@ -435,7 +436,10 @@ impl CodexMessageProcessor {
                 code: INTERNAL_ERROR_CODE,
                 message: format!("failed to reload config: {err}"),
                 data: None,
-            })
+            })?;
+        config.codex_linux_sandbox_exe = self.arg0_paths.codex_linux_sandbox_exe.clone();
+        config.main_execve_wrapper_exe = self.arg0_paths.main_execve_wrapper_exe.clone();
+        Ok(config)
     }
 
     fn current_cloud_requirements(&self) -> CloudRequirementsLoader {
@@ -1792,7 +1796,7 @@ impl CodexMessageProcessor {
             None => self.config.permissions.sandbox_policy.get().clone(),
         };
 
-        let codex_linux_sandbox_exe = self.config.codex_linux_sandbox_exe.clone();
+        let codex_linux_sandbox_exe = self.arg0_paths.codex_linux_sandbox_exe.clone();
         let outgoing = self.outgoing.clone();
         let request_for_task = request;
         let sandbox_cwd = self.config.cwd.clone();
@@ -1857,7 +1861,8 @@ impl CodexMessageProcessor {
             approval_policy,
             sandbox_mode,
             model_provider,
-            codex_linux_sandbox_exe: self.codex_linux_sandbox_exe.clone(),
+            codex_linux_sandbox_exe: self.arg0_paths.codex_linux_sandbox_exe.clone(),
+            main_execve_wrapper_exe: self.arg0_paths.main_execve_wrapper_exe.clone(),
             base_instructions,
             developer_instructions,
             compact_prompt,
@@ -2111,7 +2116,8 @@ impl CodexMessageProcessor {
             approval_policy: approval_policy
                 .map(codex_app_server_protocol::AskForApproval::to_core),
             sandbox_mode: sandbox.map(SandboxMode::to_core),
-            codex_linux_sandbox_exe: self.codex_linux_sandbox_exe.clone(),
+            codex_linux_sandbox_exe: self.arg0_paths.codex_linux_sandbox_exe.clone(),
+            main_execve_wrapper_exe: self.arg0_paths.main_execve_wrapper_exe.clone(),
             base_instructions,
             developer_instructions,
             personality,
@@ -4325,7 +4331,8 @@ impl CodexMessageProcessor {
                     approval_policy,
                     sandbox_mode,
                     model_provider,
-                    codex_linux_sandbox_exe: self.codex_linux_sandbox_exe.clone(),
+                    codex_linux_sandbox_exe: self.arg0_paths.codex_linux_sandbox_exe.clone(),
+                    main_execve_wrapper_exe: self.arg0_paths.main_execve_wrapper_exe.clone(),
                     base_instructions,
                     developer_instructions,
                     compact_prompt,
@@ -4336,7 +4343,8 @@ impl CodexMessageProcessor {
             }
             None => (
                 ConfigOverrides {
-                    codex_linux_sandbox_exe: self.codex_linux_sandbox_exe.clone(),
+                    codex_linux_sandbox_exe: self.arg0_paths.codex_linux_sandbox_exe.clone(),
+                    main_execve_wrapper_exe: self.arg0_paths.main_execve_wrapper_exe.clone(),
                     ..Default::default()
                 },
                 None,
@@ -4520,7 +4528,8 @@ impl CodexMessageProcessor {
                     approval_policy,
                     sandbox_mode,
                     model_provider,
-                    codex_linux_sandbox_exe: self.codex_linux_sandbox_exe.clone(),
+                    codex_linux_sandbox_exe: self.arg0_paths.codex_linux_sandbox_exe.clone(),
+                    main_execve_wrapper_exe: self.arg0_paths.main_execve_wrapper_exe.clone(),
                     base_instructions,
                     developer_instructions,
                     compact_prompt,
@@ -4532,7 +4541,8 @@ impl CodexMessageProcessor {
             }
             None => (
                 ConfigOverrides {
-                    codex_linux_sandbox_exe: self.codex_linux_sandbox_exe.clone(),
+                    codex_linux_sandbox_exe: self.arg0_paths.codex_linux_sandbox_exe.clone(),
+                    main_execve_wrapper_exe: self.arg0_paths.main_execve_wrapper_exe.clone(),
                     ..Default::default()
                 },
                 None,