Links: key the image check cache on the resolved file, not the link text

A relative link names another file once the document is saved elsewhere,
so a status remembered for the old file must not answer for the new one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/links.rs

@@ -155,13 +155,13 @@ pub fn link_missing(a: &designcraft_doc::Asset, document: Option<&Path>) -> bool
     }
 }
 
-/// Link status of an asset in the document at `document`. Only a regular file is compared, so a
-/// link to a device (`/dev/zero`) or a FIFO is missing rather than read.
-/// Linked images checked this session: (asset, the identity of its bytes, link) → (the file's size
-/// and time when it was read, whether it matched the bytes). The bytes' identity (their `Arc`'s
-/// address, as the render cache keys them) changes with every relink, update or undo, so a
-/// remembered answer can never describe other bytes.
-pub(crate) type ImageChecks = std::collections::HashMap<(AssetId, usize, String), (Fingerprint, bool)>;
+/// Linked images checked this session: (asset, the identity of its bytes, the file its link
+/// resolves to) → (the file's size and time when it was read, whether it matched the bytes). The
+/// resolved file, not the link text, is the key: a relative link names another file once the
+/// document is saved elsewhere. The bytes' identity (their `Arc`'s address, as the render cache
+/// keys them) changes with every relink, update or undo, so a remembered answer can never
+/// describe other bytes.
+pub(crate) type ImageChecks = std::collections::HashMap<(AssetId, usize, std::path::PathBuf), (Fingerprint, bool)>;
 
 /// Link status of a placed graphic (`ok`, `modified`, `missing`, `embedded`), reading the file
 /// only when its size is the asset's and its time isn't the one remembered from the last read
@@ -188,7 +188,7 @@ pub(crate) fn status_cached(a: &designcraft_doc::Asset, document: Option<&Path>,
         if now.size != a.data.len() as u64 {
             return "modified";
         }
-        let key = (a.id, Arc::as_ptr(&a.data) as usize, link.clone());
+        let key = (a.id, Arc::as_ptr(&a.data) as usize, path.clone());
         if let Some((at, same)) = checks.get(&key)
             && *at == now
         {

crates/engine/src/lib.rs

@@ -437,7 +437,8 @@ pub struct Session {
     pub(crate) text_link_checks: std::collections::HashMap<String, (designcraft_doc::Fingerprint, String)>,
     /// Linked images checked against their files this session (`links.list` polls twice a second):
     /// a file of the recorded size and time isn't read again.
-    pub(crate) image_link_checks: std::collections::HashMap<(designcraft_doc::AssetId, usize, String), (designcraft_doc::Fingerprint, bool)>,
+    pub(crate) image_link_checks:
+        std::collections::HashMap<(designcraft_doc::AssetId, usize, std::path::PathBuf), (designcraft_doc::Fingerprint, bool)>,
 }
 
 impl Default for Session {