Trim compiled unit export surface

docs/wasm-runtime-architecture.md

@@ -131,6 +131,15 @@ __uce_<base>[_<sanitize(suffix)>]
 | `exists` | probe only — resolves the unit, loads nothing |
 
 `sanitize_symbol_suffix()` keeps `[A-Za-z0-9_]` (mirrors `ascii_safe_name`).
+Unit code is hidden by default so the linker can discard loaded helpers that the
+unit does not use. Handler macros and the explicit `EXPORT` directive are the
+only application symbols promoted to default visibility; generated request
+binding and constructor exports remain part of the runtime ABI. Debug sections
+are removed after linking while the wasm name section is retained for runtime
+traces. This keeps each side module's code and public ABI local to its actual
+handler responsibility instead of duplicating every helper from a loaded app
+library.
+
 `wasm_resolve_target(unit, handler)` (`src/wasm/core.cpp`) resolves the source
 path and looks up the export's funcref slot; `exists` lets callers probe a unit
 without instantiating it.