feat(core)!: replace RenderResult with buffered output model

Remove `Deref<Target=str>` and `render_text:String` in favor of
`render_buffer:Vec<(String, RenderResultMode)>` and an
`immediate_output`
flag. Add `RenderResultMode` enum, `r_eprint!`/`r_eprintln!` macros, and
new buffer manipulation methods (`append_to_buffer`, `eprint`, etc.).
Update `Display` to trim output and remove trailing newline. Migrate all
callers and tests away from `Deref` usage.

1 files changed, 4 insertions, 4 deletions

diff --git a/mingling/src/example_docs.rs b/mingling/src/example_docs.rs
index bdefb5a..3b36f00 100644
--- a/mingling/src/example_docs.rs
+++ b/mingling/src/example_docs.rs
@@ -2796,25 +2796,25 @@ pub mod example_structural_renderer {}
 ///     #[test]
 ///     fn test_render_result_name() {
 ///         let r = render_result_name(ResultName::new("Peter".into()));
-///         assert_eq!(r.to_string().as_str(), "Hello, Peter!\n")
+///         assert_eq!(r.to_string().as_str(), "Hello, Peter!")
 ///     }
 ///
 ///     #[test]
 ///     fn test_render_error_no_name_provided() {
 ///         let r = render_error_no_name_provided(ErrorNoNameProvided::default());
-///         assert_eq!(r.to_string().as_str(), "No name provided\n")
+///         assert_eq!(r.to_string().as_str(), "No name provided")
 ///     }
 ///
 ///     #[test]
 ///     fn test_render_error_name_not_available() {
 ///         let r = render_error_name_not_available(ErrorNameNotAvailable::default());
-///         assert_eq!(r.to_string().as_str(), "Name not available\n")
+///         assert_eq!(r.to_string().as_str(), "Name not available")
 ///     }
 ///
 ///     #[test]
 ///     fn test_render_error_name_too_long() {
 ///         let r = render_error_name_too_long(ErrorNameTooLong::new(17));
-///         assert_eq!(r.to_string().as_str(), "Name too long: 17 > 10\n")
+///         assert_eq!(r.to_string().as_str(), "Name too long: 17 > 10")
 ///     }
 ///     // --------- IMPORTANT ---------
 /// }