fix(docx): write a body panel's table indent even when it is 0

CHANGELOG.md

@@ -8,6 +8,13 @@ follow semantic versioning; release dates are ISO 8601.
 
 ### Public API
 
+- **A panel bled to the paper's edge stands where the page puts it in Word.** A panel's
+  table indent places its text, and an indent of 0 was not written. A panel whose negative
+  margin takes its fill to the paper's edge and whose padding takes its text back to the
+  margin has exactly that indent, and with none Word puts the table's edge on the margin:
+  `IndigoProposal`'s about band, fill and text, stood 27.6pt right of the page's. The indent is
+  now written in the body even when it is 0. LibreOffice already set the band where the page
+  does.
 - **A drawing over text in a row nested through a one-layer stack takes its room in DOCX.**
   A row cannot sit in a row cell, so templates wrap one in a layer stack of one layer; the
   row is written in the flow, and a drawing in it is drawn where the page puts it. Its room

docs/recipes/docx-export.md

@@ -387,6 +387,10 @@ How it lands:
   by the other half, so the text and the border land where the page draws them. Measured
   in LibreOffice against the engine's render at 96 dpi, the band, a 3pt accent bar and the
   text of a card land within a pixel of the page's.
+- **Indent.** In the body the table's `w:tblInd` places its cell's text, less half its left
+  border, and is written even when it is 0 — a panel bled to the paper's edge by a negative
+  margin its padding takes back. Unwritten, Word 16 puts the table's edge on the margin and the
+  text a padding further in (measured).
 - **Nesting.** A panel inside a panel is a table inside its cell. So is a row, with no fill
   of its own, so the panel shows through it. A table keeps its own cell fills, and a cell
   no style fills is written white, as the page draws it on the card. Word draws a table's

render-docx/src/main/java/com/demcha/compose/document/backend/semantic/docx/DocxSemanticBackend.java

@@ -3278,7 +3278,11 @@ private void writePanelPiece(XWPFDocument document, DocumentNode node, Container
             holdRowAtLeast(table.getRow(0), shape.outline().height() - bordersOutside);
         }
 
-        if (indent != 0) {
+        // In the body it is written even when it is 0. The indent places the cell's text, less
+        // half its left border, and with none Word 16 places the table's edge on the margin
+        // instead, its text a padding further in (measured): IndigoProposal's about band, bled to the paper's edge by a negative margin its
+        // padding takes back, stood 27.6pt right of the page's, fill and text.
+        if (indent != 0 || currentCell == null) {
             CTTblPr tableProperties = table.getCTTbl().getTblPr();
             CTTblWidth tableIndent = tableProperties.isSetTblInd()
                     ? tableProperties.getTblInd()

render-docx/src/test/java/com/demcha/compose/document/backend/semantic/docx/DocxPanelInsetTest.java

@@ -45,6 +45,26 @@ void aPaddedPanelsTextIsHeldInByTheCellNotByAnIndent() throws Exception {
         }
     }
 
+    @Test
+    void aPanelBledToThePaperEdgeWritesItsIndentOfNothing() throws Exception {
+        // A negative margin takes the fill to the paper's edge and the padding takes the text
+        // back to the page margin: the indent placing the text is 0. Unwritten, Word puts the
+        // table's edge on the margin and the text a padding further in (measured, 27.6pt).
+        try (XWPFDocument document = DocxExports.withLayout(400, 300, 30, page -> page
+                .addSection(s -> s.fillColor(SURFACE)
+                        .margin(new DocumentInsets(0, -30, 0, -30))
+                        .padding(new DocumentInsets(0, 0, 0, 30))
+                        .addParagraph(p -> p.text("Band"))))) {
+            var properties = document.getTables().get(0).getCTTbl().getTblPr();
+
+            assertThat(properties.isSetTblInd()).as("written, though it is nothing").isTrue();
+            assertThat(DocxTwips.of(properties.getTblInd().getW())).isZero();
+            assertThat(DocxTwips.of(document.getTables().get(0).getRow(0).getCell(0).getCTTc().getTcPr()
+                    .getTcMar().getLeft().getW()))
+                    .as("the text at the margin, the fill from the paper's edge").isEqualTo(30 * 20L);
+        }
+    }
+
     @Test
     void anUnpaintedContainerStillHoldsItsTextIn() throws Exception {
         try (XWPFDocument document = DocxExports.withLayout(400, 300, 30, page -> page