Sheet sets: import statuses, view navigation fields, drawing lock files

Import Layouts as Sheets shows the reference's statuses (already part of
a sheet set / may belong to another sheet set / available) and Browse
replaces the list; the Field dialog SheetView tree lists sheet views with
their properties, scale formats and hyperlinks; drawings open in tabs get
.dwl/.dwl2 lock files that other instances read as open; the codec pin
moves to the revision with sheet views and the default output folder.

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

src/locale_catalog.rs

@@ -50,6 +50,8 @@ pub(super) fn message_attribute(source: &str) -> Option<(&'static str, &'static
         "New sheet location" => Some(("view", "ss-new-sheet-location")),
         "Remove Subset" => Some(("view", "ss-remove-subset")),
         "Rename Subset..." => Some(("view", "ss-rename-subset")),
+        "This layout is already part of a sheet set - not available for import." => Some(("view", "ss-layout-already-part")),
+        "Warning: this layout may belong to another sheet set." => Some(("view", "ss-layout-may-belong")),
         "missing" => Some(("view", "ss-status-missing")),
         "open" => Some(("view", "ss-status-open")),
         "View by category" => Some(("view", "ss-view-by-category")),
@@ -70,7 +72,6 @@ pub(super) fn message_attribute(source: &str) -> Option<(&'static str, &'static
         "Prefix with sheet number" => Some(("view", "ss-prefix-with-sheet-number")),
         "Rename drawing file to match:" => Some(("view", "ss-rename-drawing-file-to-match")),
         "Available for import" => Some(("view", "ss-available-for-import")),
-        "Belongs to sheet set {}" => Some(("view", "ss-belongs-to-sheet-set")),
         "Drawings" => Some(("view", "ss-drawings")),
         "Select drawing files containing layouts" => Some(("view", "ss-select-drawing-files-containing-layouts")),
         "Browse for Drawings..." => Some(("view", "ss-browse-for-drawings")),