refactor(ffi): audit and remove unjustified #[allow(dead_code)] annotations

Every reachable pub(crate) helper (convert/ helpers, tree/flatten::flatten_tree,
error::{set_last_error, clear_last_error, last_error_code, error_code_to_result})
now stands without the annotation — these are all called from #[no_mangle]
entrypoints and rustc sees them correctly.

Move the three test-only last_error readers (last_error_message_str,
last_error_suggestion_str, last_error_platform_detail_str) plus the
MessageSource::to_owned_string helper into #[cfg(test)] scope. They were
only ever used by tests; having them stand at module scope required the
annotation and muddied the public-surface read.

Zero #[allow(dead_code)] remains in crates/ffi/src/. Tree still compiles,
27 tests still pass, cbindgen header symbol set unchanged.

crates/ffi/src/convert/app.rs

@@ -4,7 +4,6 @@ use agent_desktop_core::node::AppInfo;
 use std::os::raw::c_char;
 use std::ptr;
 
-#[allow(dead_code)]
 pub(crate) fn app_info_to_c(a: &AppInfo) -> AdAppInfo {
     AdAppInfo {
         name: string_to_c(&a.name),
@@ -13,7 +12,6 @@ pub(crate) fn app_info_to_c(a: &AppInfo) -> AdAppInfo {
     }
 }
 
-#[allow(dead_code)]
 pub(crate) unsafe fn free_app_info_fields(a: &mut AdAppInfo) {
     free_c_string(a.name as *mut c_char);
     free_c_string(a.bundle_id as *mut c_char);

crates/ffi/src/convert/rect.rs

@@ -1,7 +1,6 @@
 use crate::types::AdRect;
 use agent_desktop_core::node::Rect;
 
-#[allow(dead_code)]
 pub(crate) fn rect_to_c(r: &Rect) -> AdRect {
     AdRect {
         x: r.x,

crates/ffi/src/convert/string.rs

@@ -2,7 +2,6 @@ use std::ffi::{CStr, CString};
 use std::os::raw::c_char;
 use std::ptr;
 
-#[allow(dead_code)]
 pub(crate) fn string_to_c(s: &str) -> *mut c_char {
     match CString::new(s) {
         Ok(cs) => cs.into_raw(),
@@ -10,7 +9,6 @@ pub(crate) fn string_to_c(s: &str) -> *mut c_char {
     }
 }
 
-#[allow(dead_code)]
 pub(crate) fn opt_string_to_c(s: Option<&str>) -> *mut c_char {
     match s {
         Some(s) => string_to_c(s),
@@ -18,14 +16,12 @@ pub(crate) fn opt_string_to_c(s: Option<&str>) -> *mut c_char {
     }
 }
 
-#[allow(dead_code)]
 pub(crate) unsafe fn free_c_string(ptr: *mut c_char) {
     if !ptr.is_null() {
         drop(CString::from_raw(ptr));
     }
 }
 
-#[allow(dead_code)]
 pub(crate) unsafe fn c_to_str<'a>(ptr: *const c_char) -> Option<&'a str> {
     if ptr.is_null() {
         return None;

crates/ffi/src/convert/surface.rs

@@ -4,7 +4,6 @@ use agent_desktop_core::node::SurfaceInfo;
 use std::os::raw::c_char;
 use std::ptr;
 
-#[allow(dead_code)]
 pub(crate) fn surface_info_to_c(s: &SurfaceInfo) -> AdSurfaceInfo {
     AdSurfaceInfo {
         kind: string_to_c(&s.kind),
@@ -13,7 +12,6 @@ pub(crate) fn surface_info_to_c(s: &SurfaceInfo) -> AdSurfaceInfo {
     }
 }
 
-#[allow(dead_code)]
 pub(crate) unsafe fn free_surface_info_fields(s: &mut AdSurfaceInfo) {
     free_c_string(s.kind as *mut c_char);
     free_c_string(s.title as *mut c_char);

crates/ffi/src/convert/window.rs

@@ -5,7 +5,6 @@ use agent_desktop_core::node::WindowInfo;
 use std::os::raw::c_char;
 use std::ptr;
 
-#[allow(dead_code)]
 pub(crate) fn window_info_to_c(w: &WindowInfo) -> AdWindowInfo {
     let (bounds, has_bounds) = match &w.bounds {
         Some(r) => (rect_to_c(r), true),
@@ -30,7 +29,6 @@ pub(crate) fn window_info_to_c(w: &WindowInfo) -> AdWindowInfo {
     }
 }
 
-#[allow(dead_code)]
 pub(crate) unsafe fn free_window_info_fields(w: &mut AdWindowInfo) {
     free_c_string(w.id as *mut c_char);
     free_c_string(w.title as *mut c_char);

crates/ffi/src/error.rs

@@ -33,6 +33,7 @@ impl MessageSource {
         }
     }
 
+    #[cfg(test)]
     fn to_owned_string(&self) -> String {
         match self {
             MessageSource::Owned(cs) => cs.to_string_lossy().into_owned(),
@@ -54,7 +55,6 @@ thread_local! {
     static LAST_ERROR: RefCell<Option<StoredError>> = const { RefCell::new(None) };
 }
 
-#[allow(dead_code)]
 fn error_code_to_result(code: &ErrorCode) -> AdResult {
     match code {
         ErrorCode::PermDenied => AdResult::ErrPermDenied,
@@ -72,7 +72,6 @@ fn error_code_to_result(code: &ErrorCode) -> AdResult {
     }
 }
 
-#[allow(dead_code)]
 pub(crate) fn set_last_error(err: &AdapterError) {
     let code = error_code_to_result(&err.code);
     let message = match CString::new(err.message.as_str()) {
@@ -94,14 +93,12 @@ pub(crate) fn set_last_error(err: &AdapterError) {
     });
 }
 
-#[allow(dead_code)]
 pub(crate) fn clear_last_error() {
     LAST_ERROR.with(|cell| {
         *cell.borrow_mut() = None;
     });
 }
 
-#[allow(dead_code)]
 pub(crate) fn last_error_code() -> AdResult {
     LAST_ERROR.with(|cell| {
         cell.borrow()
@@ -111,33 +108,6 @@ pub(crate) fn last_error_code() -> AdResult {
     })
 }
 
-#[allow(dead_code)]
-pub(crate) fn last_error_message_str() -> Option<String> {
-    LAST_ERROR.with(|cell| cell.borrow().as_ref().map(|e| e.message.to_owned_string()))
-}
-
-#[allow(dead_code)]
-pub(crate) fn last_error_suggestion_str() -> Option<String> {
-    LAST_ERROR.with(|cell| {
-        cell.borrow().as_ref().and_then(|e| {
-            e.suggestion
-                .as_ref()
-                .map(|s| s.to_string_lossy().into_owned())
-        })
-    })
-}
-
-#[allow(dead_code)]
-pub(crate) fn last_error_platform_detail_str() -> Option<String> {
-    LAST_ERROR.with(|cell| {
-        cell.borrow().as_ref().and_then(|e| {
-            e.platform_detail
-                .as_ref()
-                .map(|s| s.to_string_lossy().into_owned())
-        })
-    })
-}
-
 #[no_mangle]
 pub extern "C" fn ad_last_error_code() -> AdResult {
     last_error_code()
@@ -177,6 +147,30 @@ pub extern "C" fn ad_last_error_platform_detail() -> *const c_char {
 mod tests {
     use super::*;
 
+    fn last_error_message_str() -> Option<String> {
+        LAST_ERROR.with(|cell| cell.borrow().as_ref().map(|e| e.message.to_owned_string()))
+    }
+
+    fn last_error_suggestion_str() -> Option<String> {
+        LAST_ERROR.with(|cell| {
+            cell.borrow().as_ref().and_then(|e| {
+                e.suggestion
+                    .as_ref()
+                    .map(|s| s.to_string_lossy().into_owned())
+            })
+        })
+    }
+
+    fn last_error_platform_detail_str() -> Option<String> {
+        LAST_ERROR.with(|cell| {
+            cell.borrow().as_ref().and_then(|e| {
+                e.platform_detail
+                    .as_ref()
+                    .map(|s| s.to_string_lossy().into_owned())
+            })
+        })
+    }
+
     #[test]
     fn test_no_error_initially() {
         clear_last_error();

crates/ffi/src/tree/flatten.rs

@@ -4,7 +4,6 @@ use agent_desktop_core::node::AccessibilityNode;
 use std::os::raw::c_char;
 use std::ptr;
 
-#[allow(dead_code)]
 pub(crate) fn flatten_tree(root: &AccessibilityNode) -> AdNodeTree {
     let mut flat: Vec<AdNode> = Vec::new();
     flatten_recursive(root, -1, &mut flat);
@@ -20,7 +19,6 @@ pub(crate) fn flatten_tree(root: &AccessibilityNode) -> AdNodeTree {
     AdNodeTree { nodes, count }
 }
 
-#[allow(dead_code)]
 fn flatten_recursive(node: &AccessibilityNode, parent_index: i32, flat: &mut Vec<AdNode>) {
     let my_index = flat.len() as i32;
 
@@ -62,7 +60,6 @@ fn flatten_recursive(node: &AccessibilityNode, parent_index: i32, flat: &mut Vec
     }
 }
 
-#[allow(dead_code)]
 fn strings_to_c_array(strings: &[String]) -> (*mut *mut c_char, u32) {
     if strings.is_empty() {
         return (ptr::null_mut(), 0);