Add ranked tool discovery to JavaScript code mode (#51209)

## What changed

- Add the default-disabled `code_mode_tool_search` feature to expose `await tools.tool_search({query: "...", limit: 8})` in code mode when the model supports tool search.
- Return BM25-ranked deferred tools as `{tools: [{name, description}]}`, including callable names and TypeScript declarations for use in later code cells.
- Filter results through the current step's nested-tool policy before applying the limit, preserving namespace restrictions, normalized identities, description prefixes, and schema budgets.
- Add ranked-search guidance while retaining `ALL_TOOLS` catalog discovery and description overrides.

## Testing

Add coverage for feature and model-capability gating, namespace restrictions, argument validation, schema budgets, and discovery followed by deferred MCP and dynamic tool calls. Extend the scenario snapshot to cover search, invocation, yielding, and completion through `wait`.

GitOrigin-RevId: 092a29dd5f0773c518f53a001b9cafb917422f13

codex-rs/tools/src/code_mode.rs

@@ -223,7 +223,38 @@ fn code_mode_tool_definitions_for_spec(
                 }
             })
             .collect(),
-        ToolSpec::ToolSearch { .. } | ToolSpec::WebSearch { .. } => Vec::new(),
+        ToolSpec::ToolSearch { parameters, .. } => {
+            let name = spec.name().to_string();
+            vec![CodeModeToolDefinition {
+                tool_name: ToolName::plain(name.clone()),
+                name,
+                description: codex_code_mode::TOOL_SEARCH_GUIDANCE.to_string(),
+                kind: CodeModeToolKind::Function,
+                input_schema: serde_json::to_value(parameters).ok(),
+                input_schema_max_bytes: Some(effective_input_schema_max_bytes(
+                    parameters.mcp_input_schema_max_bytes,
+                    code_mode_input_schema_max_bytes,
+                )),
+                output_schema: Some(serde_json::json!({
+                    "type": "object",
+                    "properties": {
+                        "tools": {
+                            "type": "array",
+                            "items": {
+                                "type": "object",
+                                "properties": {
+                                    "name": { "type": "string" },
+                                    "description": { "type": "string" }
+                                },
+                                "required": ["name", "description"]
+                            }
+                        }
+                    },
+                    "required": ["tools"]
+                })),
+            }]
+        }
+        ToolSpec::WebSearch { .. } => Vec::new(),
     }
 }