fix(diagnostics): bound formatting and release ingress before callbacks

Bound UTF-8 formatting and release diagnostic ingress before invoking
callbacks. Check error-ID collisions at Rust/C++ release final link.

Validation: diagnostic tests, strict Clippy, Miri and final-link cases.

firmware/libs/kaptan-err-reportable-macros/src/lib.rs

@@ -1,4 +1,4 @@
-//! Attribute expansion for `kaptan-err-reportable`.
+//! Error derive and reporting-attribute expansion for `kaptan-err-reportable`.
 
 use proc_macro::TokenStream;
 use quote::{format_ident, quote};
@@ -12,8 +12,12 @@ use syn::{
 /// [`core::error::Error`] for an explicitly numbered error enum.
 ///
 /// Every variant must declare a stable nonzero
-/// `#[kaptan_error(id = ...)]`. Duplicate IDs fail compilation within an enum
-/// or crate and fail final linking when they originate in different crates.
+/// `#[kaptan_error(id = ...)]`. The derive rejects duplicates within an enum.
+/// Across enums, duplicate IDs emit the same reserved symbol. Collision detection
+/// requires both defining objects to participate in compilation or final linking.
+/// Unextracted archive members are not checked, so catalog allocation still needs
+/// review. The fixture guide in `tests/final_link.md` describes Rust release-LTO
+/// and native Linux checks. Embedded linker combinations need their own checks.
 #[proc_macro_derive(KaptanError, attributes(kaptan_error))]
 pub fn derive_kaptan_error(input: TokenStream) -> TokenStream {
     let input = parse_macro_input!(input as DeriveInput);