Key the set-price menu modes on the set instead of the service-request block (ADR 0019)

"Set mit Preis" / "Nur Set mit Preis" collapsed every block into an inserted
"Gesamtumfang pauschal" row, nulled/removed all lines and cleared the user-defined
set structure. Both modes now convert every still-unconverted top-level set:
the set line takes the sum of its subtree, its members render without a price
(setprice) or are removed from itm + items (setonly); lines outside a set stay
individually priced and several sets stay separate lines. Nested sets are priced
once via their top-level set. One conversion primitive (ConvertSetHeader) now
backs all three triggers; item.setprice is a no-op on an already-converted set
(a repeated delta used to reset the set price to 0). The header's price_net is
mirrored too (flat PDF path unit price), and Build treats a null total_net as
"no price" like the flat path. The editor checks for a set before offering the
modes and the menu entry stays available for sets added later.

ADR 0009 is superseded by 0019; INVOICE_SET_PRICING.md rewritten accordingly.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Fuchs/code/FuchsPdf.cs

@@ -778,9 +778,11 @@ public static class FuchsPdf
         // Blocks without any set items are unaffected and always render flat.
         var setMode = InvoiceSetPricing.ModeFromInvoiceOptions(inv.InvoiceRegistration?.getString("InvoiceOptions"));
 
-        // Function-1 (SetItmId-linked) sets still collapse via Build; block-mode sets (ADR 0009)
-        // and plain blocks render flat — their set row is emphasised on its own and nulled
-        // members map to blank cells (see MapItemToLine).
+        // Blocks that carry a set (a line pointing at a set header via setId) render through Build,
+        // which blanks/drops the members of a converted set; blocks without any set render flat —
+        // nulled prices map to blank cells either way (see MapItemToLine). Since ADR 0019 the menu
+        // modes convert per set (not per block) and leave non-set lines individually priced, so both
+        // paths print exactly what the editor shows.
         var blockLines = inv.InvoiceBlocks
             .Select(block => InvoiceSetPricing.HasSetMembers(block.Items)
                 ? InvoiceSetPricing.Build(block.Items, setMode)

Fuchs/code/InvoiceSetPricing.cs

@@ -97,10 +97,10 @@ public static class InvoiceSetPricing
         items.Any(IsSetHeader) || items.Any(i => !string.IsNullOrEmpty(SetIdOf(i)));
 
     /// <summary>
-    /// True if the block carries a <c>SetItmId</c>-linked set (a member points at a header via
-    /// <c>setId</c>) — i.e. the function-1 "set-item switch" grouping. This is the only case that
-    /// still routes through <see cref="Build"/>; the two menu modes (ADR 0009) clear <c>setId</c>
-    /// and render flat (their inserted set row is emphasised on its own, members null out to blank).
+    /// True if the block carries a set (a line points at a set header via <c>setId</c>) — the only
+    /// case that routes through <see cref="Build"/>. Since ADR 0019 every set-price operation — the
+    /// inline set-item switch and both menu modes — preserves that membership, so this is what
+    /// renders their result too; a block of lines that belong to no set renders flat.
     /// </summary>
     public static bool HasSetMembers(IEnumerable<Dictionary<string, object?>> items) =>
         items.Any(i => !string.IsNullOrEmpty(SetIdOf(i)));
@@ -227,6 +227,10 @@ public static class InvoiceSetPricing
     {
         FuchsPdf.ParseDec(i.no("price_net", 0), out decimal price);
         FuchsPdf.ParseDec(i.no("total_net", 0), out decimal total);
+        // A JSON-null total_net is "no price" (ADR 0009/0019) — an empty cell, never 0,00 € — exactly
+        // as the flat path (FuchsPdf.MapItemToLine) treats it. Matters for a price-nulled member whose
+        // set was later hand-edited back to 0 (and so reads as unconverted again).
+        bool hasPrice = !i.TryGetValue("total_net", out var tv) || tv != null;
         return new InvoiceSetLine
         {
             Id        = i.nz("id", ""),
@@ -235,7 +239,7 @@ public static class InvoiceSetPricing
             Qty       = i.nz("qty", "1"),
             PriceNet  = price,
             TotalNet  = total,
-            ShowPrice = showPrice && !IsNoPriceLine(i),  // headings/free text print no price
+            ShowPrice = showPrice && hasPrice && !IsNoPriceLine(i),  // headings/free text print no price
             Numbered  = !IsNoPriceLine(i),               // …but are still numbered unless heading/free-text
             IsSetHeader = false,
             Level     = level