fix(docx): hold a container's content inside its sides

[DemchaAV]

Why

A container's margin and padding hold its content in from its edges, and on the page a card's text sits inside the card. The DOCX export carried a container's top and bottom edge as paragraph spacing, but never its sides.

In LibreOffice, a filled card with 14pt padding and a left accent had:

• its text flush with the page margin, touching the card's edge;
• the accent bar right against the first letter;
• wrapping at a different point than the page, because the text had 28pt more width.

What changed

• Content inset. writeContainerBody accumulates each container's left and right margin plus padding (insetLeft / insetRight), restoring them afterwards. newBodyParagraph writes the total as w:ind (applyInset), so nested containers add up. A paragraph outside any container gets no w:ind, as before.
• Panel edges at the card's edge, not the text's. Word draws a side border its w:space outside the text and shades the paragraph out to that border. In applyContainerPaint:
  • A panel's left and right borders are spaced by its padding. The accent bar lands at the card's edge and the fill reaches it.
  • A filled side with no border gets a hairline (w:sz="2") in the fill's own colour, spaced the same way, so the band reaches that edge too.
  • w:space stops at 31pt, so a wider padding brings the band's edge in by the difference.
• Numbered list items. A paragraph's own w:ind replaces its numbering level's, which would drop the hanging indent.
  • indentListItemInside writes the inset plus the level's indent, and keeps the hanging.
  • It spaces the item's left border from where the editor measures a hanging paragraph's border: its first line, one nesting step per level. With the whole level indent, the first attempt put the bar 9pt outside the card on every item (measured).
• The panel records its edge on entry (ContainerPaint.at), and a side border is spaced by the distance from the text to that edge. A padded section nested in a card therefore keeps the card's bar at the card's edge. Spacing by the panel's own padding stepped the bar in by the inner padding.
• Rows and tables move in with the text. indentTable writes w:tblInd for body tables and rows once they are written. The value is the inset plus the first cell's written margin: LibreOffice measures w:tblInd to the first cell's text, so the inset alone left the border 4pt short. Measured, the table's border lands on the card's text line, as on the page.
• Pictures and row fallbacks use the width left between the insets (availableWidth). Before, a full-width picture in a padded card ran past the right margin.
• A nested numbered item (depth > 0) spaces its border from its first line even when there is no inset.
• Cells start from their own edge. writeCellNode resets the inset and restores it, because a table's cells are not inset by the containers around the table.
• Recipe updated. "What a panel keeps and loses" now says what carries, including the 31pt limit. CHANGELOG under v2.5.0.

Not in this change: the panel is still paragraph-by-paragraph. Word has no element that wraps a run of paragraphs, so a filled card is shading and borders on each paragraph. In LibreOffice this leaves several gaps:

• The accent bar breaks beside rows and tables, and between paragraphs whose indents differ.
• The band has white gaps where vertical spacing sits between blocks, and none under a table.
• The top and bottom padding stay outside the shading.

Spaced top and bottom borders were tried and broke the card into pieces around a list. Writing a painted card as a one-cell table would carry all of it; that is proposed as a follow-up. The inset logic here stays useful either way, for unpainted containers and for aligning rows, tables and pictures.

Verification

In an editor. A filled card with 14pt padding and a 3pt left accent, holding two paragraphs and a bullet list, converted with LibreOffice and compared with the engine's PNG:

• the accent bar is at the card's edge, continuous past the list;
• the text and the bullets start 14pt in, with the list's continuation lines hanging;
• lines wrap at the same words as the page.

Gate. Full reactor gate (clean verify over core, render-pdf/docx/pptx, templates, testing, qa, coverage) → BUILD SUCCESS. Examples after install: 93 green. The committed word-export-companion.docx did not move.

New DocxPanelInsetTest (12):

• a padded panel: w:ind 14pt on both sides, the accent spaced 14, a fill-coloured right hairline spaced 14;
• an unpainted padded container still indents its text;
• nested containers add up;
• a list item in a panel: w:ind is inset + 180 twips, hanging 180, and its border is spaced 14;
• a paragraph outside any container gets no w:ind;
• a cell inside a padded panel starts from its own edge;
• a 40pt padding caps the border space at 31;
• a padded section inside a panel keeps the panel's bar at the panel's edge (space 24);
• a row and a table in a padded section get w:tblInd = inset + first-cell margin;
• a table outside any container has no w:tblInd;
• an 800pt picture in a padded section fits the 312pt left between the insets;
• a nested list item's border is spaced inset + one nesting step.

Sabotage checks:

• spacing list borders by the whole level indent fails the list test;
• dropping the cell reset fails the cell test;
• dropping indentTable, or sizing pictures to the page's width, fails the matching tests.

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