fix(docx): keep a card's paint off the paragraphs in its table's cells

[DemchaAV]

Why

A filled or bordered card is written by painting every paragraph inside it (w:shd, w:pBdr), since Word has no element that wraps a run of paragraphs.

A table inside the card writes its plain-text cells directly. A cell built from a node (DocumentTableCell.node(...)) goes through newBodyParagraph, the same path as body paragraphs, and that path painted it with the card too. In a zebra table inside a filled card, the composed cell came out in the card's colour laid over its stripe. With a bordered card, the paragraph inside the cell got boxed.

What changed

• newBodyParagraph takes container paint only from containers opened inside the cell being written.
  • writeCellNode records how many containers were open when the cell began (cellPaintDepth, saved and restored around nested cells).
  • The card's own paragraphs keep their paint, and the cell's own fill (w:shd on the cell) shows as the page draws it.
  • A container opened inside the cell (a filled section as a composed cell) still paints its own paragraphs.
• writeRow asks the same question through paintHere(), which both paths share. Before, a row built into a zebra cell of a filled card shaded its own cells in the card's colour, covering the stripe. A row placed directly in a card still shades its cells with the card's fill. It no longer draws a bordered card's outline around the text of each cell, which matches the PDF: the PDF draws only the card's outline.
• A cell with no fill of its own is left alone. The engine's default cell style is white (TableCellLayoutStyle.DEFAULT), so the PDF draws such a cell white inside a card too. In Word the card's shading sits on its paragraphs and never under the table, so that cell is already white. Shading it with the card's colour would have moved Word away from the PDF.
• Recipe ("What a panel keeps and loses") and CHANGELOG under v2.5.0.

Verification

In an editor. A card with a zebra table whose last row holds a composed cell, converted with LibreOffice. The composed cell is grey like the rest of its stripe, as in the engine's PNG. Before the change its paragraph shading was the card's E6F0FF.

Gate. Full reactor gate (clean verify over core, render-pdf/docx/pptx, templates, testing, qa, coverage) → BUILD SUCCESS. Examples after install: 93 green. No committed preview moved.

New tests in DocxContainerPaintTest (12 total, +5):

• a composed cell in a filled, bordered card keeps its zebra fill, with no paragraph shading and no paragraph border;
• a row built into a zebra cell leaves its own cells unshaded;
• a row directly in a bordered card keeps shaded cells, with no border around the text in each cell;
• the card paints its paragraphs again after the table;
• a filled section inside a cell still paints its paragraph.

Reverting either path to "always paint" fails the matching test.

Found alongside, not fixed here. Two tables with nothing between them are merged into one table by LibreOffice. Their different column grids then squeeze the result, and text breaks letter by letter. I proved this by swapping tables in the XML. It affects any two consecutive tables, not only inside a card, and is the next PR.

Lane: shared-engine (render-docx). No public API change.