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.

3 files changed, 17 insertions, 5 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 ---------
 /// }
diff --git a/mingling/src/lib.rs b/mingling/src/lib.rs
index f5362d5..3539647 100644
--- a/mingling/src/lib.rs
+++ b/mingling/src/lib.rs
@@ -98,6 +98,12 @@ pub mod macros {
     /// `#[program_setup]` - Used to generate program setup
     #[cfg(feature = "extra_macros")]
     pub use mingling_macros::program_setup;
+    /// `r_eprint!` - Prints text to a `RenderResult` error buffer (without newline).
+    /// See the macro documentation for implicit vs. explicit buffer usage.
+    pub use mingling_macros::r_eprint;
+    /// `r_eprintln!` - Prints text to a `RenderResult` error buffer (with newline).
+    /// See the macro documentation for implicit vs. explicit buffer usage.
+    pub use mingling_macros::r_eprintln;
     /// `r_print!` - Prints text to a `RenderResult` buffer (without newline).
     /// See the macro documentation for implicit vs. explicit buffer usage.
     pub use mingling_macros::r_print;
@@ -229,6 +235,12 @@ pub mod prelude {
     /// Like `pack!` but also marks the type for structured output
     #[cfg(all(feature = "macros", feature = "structural_renderer"))]
     pub use mingling_macros::pack_structural;
+    /// `r_eprint!` - Prints text to a `RenderResult` error buffer (without newline).
+    /// See the macro documentation for implicit vs. explicit buffer usage.
+    pub use mingling_macros::r_eprint;
+    /// `r_eprintln!` - Prints text to a `RenderResult` error buffer (with newline).
+    /// See the macro documentation for implicit vs. explicit buffer usage.
+    pub use mingling_macros::r_eprintln;
     /// `r_print!` - Prints text to a `RenderResult` buffer (without newline).
     /// See the macro documentation for implicit vs. explicit buffer usage.
     pub use mingling_macros::r_print;
diff --git a/mingling/src/setups/repl_basic.rs b/mingling/src/setups/repl_basic.rs
index cf04372..150048b 100644
--- a/mingling/src/setups/repl_basic.rs
+++ b/mingling/src/setups/repl_basic.rs
@@ -75,7 +75,7 @@ where
     fn setup(self, program: &mut Program<C>) {
         program.with_hook(ProgramHook::empty().on_repl_receive_result(|r| {
             if !r.result.is_empty() {
-                println!("{}", r.result.trim())
+                println!("{}", r.result)
             }
         }));
     }