[mcp] Improve custom MCP elicitation (#15800)

- [x] Support don't ask again for custom MCP tool calls.
- [x] Don't run arc in yolo mode.
- [x] Run arc for custom MCP tools in always allow mode.

codex-rs/core/tests/suite/truncation.rs

@@ -371,6 +371,7 @@ async fn mcp_tool_call_output_exceeds_limit_truncated_for_model() -> Result<()>
                 disabled_tools: None,
                 scopes: None,
                 oauth_resource: None,
+                tools: HashMap::new(),
             },
         );
         config
@@ -466,6 +467,7 @@ async fn mcp_image_output_preserves_image_and_no_text_summary() -> Result<()> {
                 disabled_tools: None,
                 scopes: None,
                 oauth_resource: None,
+                tools: HashMap::new(),
             },
         );
         config
@@ -734,6 +736,7 @@ async fn mcp_tool_call_output_not_truncated_with_custom_limit() -> Result<()> {
                 disabled_tools: None,
                 scopes: None,
                 oauth_resource: None,
+                tools: HashMap::new(),
             },
         );
         config