Tables: DeckCraft's own table styles still map back to their ids

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/pptx/src/read/shapes.rs

@@ -402,8 +402,13 @@ fn table(imp: &mut Imp, part: &Part, tbl: &El) -> Table {
         t.band_col = pr.bool("bandCol").unwrap_or(false);
         if let Some(id) = pr.child("tableStyleId").map(|e| e.text()) {
             // A style the file defines is drawn from its definition (by its GUID).
+            // DeckCraft's own styles (written with GUIDs derived from their ids) map back to them.
             let up = id.trim().to_ascii_uppercase();
-            t.style = if imp.table_style_ids.contains(&up) { up } else { crate::tables::style_from_guid(id.trim()) };
+            t.style = if imp.table_style_ids.contains(&up) && !crate::tables::is_own_guid(&up) {
+                up
+            } else {
+                crate::tables::style_from_guid(id.trim())
+            };
         }
     }
     t.cols = tbl

crates/pptx/src/tables.rs

@@ -47,6 +47,12 @@ fn own_guid(style: &str) -> String {
     guid(&format!("deckcraft-table-style:{style}"))
 }
 
+/// Is `g` the GUID DeckCraft writes for one of its own styles?
+pub fn is_own_guid(g: &str) -> bool {
+    let up = g.to_ascii_uppercase();
+    deckcraft_model::table::table_styles().iter().any(|(id, _)| own_guid(id) == up)
+}
+
 /// Table style GUID → our style id (or the GUID itself when unknown).
 pub fn style_from_guid(g: &str) -> String {
     let up = g.to_ascii_uppercase();