Remove zombie tools spec module (#22820)

## Summary

- move tool_user_shell_type out of the old tools::spec module and call
it from tools directly
- attach the remaining spec planning model tests under spec_plan
- delete core/src/tools/spec.rs

## Tests

- just fmt
- cargo test -p codex-core tools::spec_plan

Note: a broader cargo test -p codex-core run on the earlier PR-head
worktree still hit the pre-existing stack overflow in
agent::control::tests::spawn_agent_fork_last_n_turns_keeps_only_recent_turns.

codex-rs/core/src/session/review.rs

@@ -46,7 +46,7 @@ pub(super) async fn spawn_review_thread(
     .with_image_generation_capability(provider_capabilities.image_generation)
     .with_web_search_capability(provider_capabilities.web_search)
     .with_unified_exec_shell_mode_for_session(
-        crate::tools::spec::tool_user_shell_type(sess.services.user_shell.as_ref()),
+        crate::tools::tool_user_shell_type(sess.services.user_shell.as_ref()),
         sess.services.shell_zsh_path.as_ref(),
         sess.services.main_execve_wrapper_exe.as_ref(),
     )

codex-rs/core/src/session/turn_context.rs

@@ -527,7 +527,7 @@ impl Session {
         .with_image_generation_capability(provider_capabilities.image_generation)
         .with_web_search_capability(provider_capabilities.web_search)
         .with_unified_exec_shell_mode_for_session(
-            crate::tools::spec::tool_user_shell_type(user_shell),
+            crate::tools::tool_user_shell_type(user_shell),
             shell_zsh_path,
             main_execve_wrapper_exe,
         )

codex-rs/core/src/tools/mod.rs

@@ -11,7 +11,6 @@ pub(crate) mod registry;
 pub(crate) mod router;
 pub(crate) mod runtimes;
 pub(crate) mod sandboxing;
-pub(crate) mod spec;
 pub(crate) mod spec_plan;
 pub(crate) mod tool_dispatch_trace;
 pub(crate) mod tool_search_entry;
@@ -47,6 +46,18 @@ pub(crate) fn flat_tool_name(tool_name: &ToolName) -> Cow<'_, str> {
     }
 }
 
+pub(crate) fn tool_user_shell_type(
+    user_shell: &crate::shell::Shell,
+) -> codex_tools::ToolUserShellType {
+    match user_shell.shell_type {
+        crate::shell::ShellType::Zsh => codex_tools::ToolUserShellType::Zsh,
+        crate::shell::ShellType::Bash => codex_tools::ToolUserShellType::Bash,
+        crate::shell::ShellType::PowerShell => codex_tools::ToolUserShellType::PowerShell,
+        crate::shell::ShellType::Sh => codex_tools::ToolUserShellType::Sh,
+        crate::shell::ShellType::Cmd => codex_tools::ToolUserShellType::Cmd,
+    }
+}
+
 /// Format the combined exec output for sending back to the model.
 /// Includes exit code and duration metadata; truncates large bodies safely.
 pub fn format_exec_output_for_model_structured(

codex-rs/core/src/tools/spec.rs

@@ -1,17 +0,0 @@
-use crate::shell::Shell;
-use crate::shell::ShellType;
-use codex_tools::ToolUserShellType;
-
-pub(crate) fn tool_user_shell_type(user_shell: &Shell) -> ToolUserShellType {
-    match user_shell.shell_type {
-        ShellType::Zsh => ToolUserShellType::Zsh,
-        ShellType::Bash => ToolUserShellType::Bash,
-        ShellType::PowerShell => ToolUserShellType::PowerShell,
-        ShellType::Sh => ToolUserShellType::Sh,
-        ShellType::Cmd => ToolUserShellType::Cmd,
-    }
-}
-
-#[cfg(test)]
-#[path = "spec_tests.rs"]
-mod tests;

codex-rs/core/src/tools/spec_plan.rs

@@ -621,6 +621,9 @@ fn code_mode_namespace_name<'a>(
         .map(|namespace_description| namespace_description.name.as_str())
 }
 
+#[cfg(test)]
+#[path = "spec_plan_model_tests.rs"]
+mod model_tests;
 #[cfg(test)]
 #[path = "spec_plan_tests.rs"]
 mod tests;

codex-rs/core/src/tools/spec_plan_model_tests.rs

@@ -4,6 +4,7 @@ use crate::shell::ShellType;
 use crate::test_support::construct_model_info_offline;
 use crate::tools::ToolRouter;
 use crate::tools::router::ToolRouterParams;
+use crate::tools::tool_user_shell_type;
 use codex_app_server_protocol::AppInfo;
 use codex_features::Feature;
 use codex_features::Features;
@@ -40,8 +41,6 @@ use std::collections::BTreeMap;
 use std::path::PathBuf;
 use std::sync::Arc;
 
-use super::*;
-
 fn mcp_tool(name: &str, description: &str, input_schema: serde_json::Value) -> rmcp::model::Tool {
     rmcp::model::Tool {
         name: name.to_string().into(),