codex-tools: extract utility tool specs (#16154)

## Why

The previous `codex-tools` migration steps moved the shared schema
models, local-host specs, collaboration specs, and related adapters out
of `codex-core`, but `core/src/tools/spec.rs` still contained a grab bag
of pure utility tool builders. Those specs do not need session state or
handler logic; they only describe wire shapes for tools that
`codex-core` already knows how to execute.

Moving that remaining low-coupling layer into `codex-tools` keeps the
migration moving in meaningful chunks and trims another large block of
passive tool-spec construction out of `codex-core` without touching the
runtime-coupled handlers.

## What changed

- extended `codex-tools` to own the pure spec builders for:
  - code-mode `exec` / `wait`
  - `js_repl` / `js_repl_reset`
- MCP resource tools `list_mcp_resources`,
`list_mcp_resource_templates`, and `read_mcp_resource`
  - utility tools `list_dir` and `test_sync_tool`
- split those builders across small module files with sibling
`*_tests.rs` coverage, keeping `src/lib.rs` exports-only
- rewired `core/src/tools/spec.rs` to call the extracted builders and
deleted the duplicated core-local implementations
- moved the direct JS REPL grammar seam test out of
`core/src/tools/spec_tests.rs` so it now lives with the extracted
implementation in `codex-tools`
- updated `codex-rs/tools/README.md` so the documented crate boundary
matches the new utility-spec surface

## Test plan

- `CARGO_TARGET_DIR=/tmp/codex-tools-utility-specs cargo test -p
codex-tools`
- `CARGO_TARGET_DIR=/tmp/codex-core-utility-specs cargo test -p
codex-core --lib tools::spec::`
- `just fix -p codex-tools -p codex-core`
- `just argument-comment-lint`

## References

- #15923
- #15928
- #15944
- #15953
- #16031
- #16047
- #16129
- #16132
- #16138
- #16141

codex-rs/tools/src/code_mode_tests.rs

@@ -1,4 +1,6 @@
 use super::augment_tool_spec_for_code_mode;
+use super::create_code_mode_tool;
+use super::create_wait_tool;
 use super::tool_spec_to_code_mode_tool_definition;
 use crate::AdditionalProperties;
 use crate::FreeformTool;
@@ -121,3 +123,89 @@ fn tool_spec_to_code_mode_tool_definition_skips_unsupported_variants() {
         None
     );
 }
+
+#[test]
+fn create_wait_tool_matches_expected_spec() {
+    assert_eq!(
+        create_wait_tool(),
+        ToolSpec::Function(ResponsesApiTool {
+            name: codex_code_mode::WAIT_TOOL_NAME.to_string(),
+            description: format!(
+                "Waits on a yielded `{}` cell and returns new output or completion.\n{}",
+                codex_code_mode::PUBLIC_TOOL_NAME,
+                codex_code_mode::build_wait_tool_description().trim()
+            ),
+            strict: false,
+            defer_loading: None,
+            parameters: JsonSchema::Object {
+                properties: BTreeMap::from([
+                    (
+                        "cell_id".to_string(),
+                        JsonSchema::String {
+                            description: Some("Identifier of the running exec cell.".to_string()),
+                        },
+                    ),
+                    (
+                        "max_tokens".to_string(),
+                        JsonSchema::Number {
+                            description: Some(
+                                "Maximum number of output tokens to return for this wait call."
+                                    .to_string(),
+                            ),
+                        },
+                    ),
+                    (
+                        "terminate".to_string(),
+                        JsonSchema::Boolean {
+                            description: Some(
+                                "Whether to terminate the running exec cell.".to_string(),
+                            ),
+                        },
+                    ),
+                    (
+                        "yield_time_ms".to_string(),
+                        JsonSchema::Number {
+                            description: Some(
+                                "How long to wait (in milliseconds) for more output before yielding again."
+                                    .to_string(),
+                            ),
+                        },
+                    ),
+                ]),
+                required: Some(vec!["cell_id".to_string()]),
+                additional_properties: Some(false.into()),
+            },
+            output_schema: None,
+        })
+    );
+}
+
+#[test]
+fn create_code_mode_tool_matches_expected_spec() {
+    let enabled_tools = vec![("update_plan".to_string(), "Update the plan".to_string())];
+
+    assert_eq!(
+        create_code_mode_tool(&enabled_tools, /*code_mode_only_enabled*/ true),
+        ToolSpec::Freeform(FreeformTool {
+            name: codex_code_mode::PUBLIC_TOOL_NAME.to_string(),
+            description: codex_code_mode::build_exec_tool_description(
+                &enabled_tools,
+                /*code_mode_only*/ true
+            ),
+            format: FreeformToolFormat {
+                r#type: "grammar".to_string(),
+                syntax: "lark".to_string(),
+                definition: r#"
+start: pragma_source | plain_source
+pragma_source: PRAGMA_LINE NEWLINE SOURCE
+plain_source: SOURCE
+
+PRAGMA_LINE: /[ \t]*\/\/ @exec:[^\r\n]*/
+NEWLINE: /\r?\n/
+SOURCE: /[\s\S]+/
+"#
+                .to_string(),
+            },
+        })
+    );
+}