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, 8 insertions, 0 deletions

diff --git a/mingling_macros/src/func/r_print.rs b/mingling_macros/src/func/r_print.rs
index e81b544..0f77b2b 100644
--- a/mingling_macros/src/func/r_print.rs
+++ b/mingling_macros/src/func/r_print.rs
@@ -60,3 +60,11 @@ pub(crate) fn r_println(input: TokenStream) -> TokenStream {
 pub(crate) fn r_print(input: TokenStream) -> TokenStream {
     expand_print(input, "print")
 }
+
+pub(crate) fn r_eprintln(input: TokenStream) -> TokenStream {
+    expand_print(input, "eprintln")
+}
+
+pub(crate) fn r_eprint(input: TokenStream) -> TokenStream {
+    expand_print(input, "eprint")
+}