fix(docx): give a table's rules out of its cells' padding where Word makes room for them

[DemchaAV]

Why

In Word, every ruled table ran taller than on the page, row by row. EditorialProposal's timeline and investment tables pushed its investment block, with the acceptance under it, onto a third page. NorthlineProposal's acceptance heading stood 12pt below its badge, which is drawn where the page puts it.

The page draws a cell's rules on its edges and steps its rows by padding and content alone. Word makes room for a table's horizontal rules. Measured through Word COM on a probe of 12.35pt text with 7pt padding:

rules	row step	one-row table
none	26.35pt	—
0.75pt	27.1pt	—
1.5pt	27.85pt	+3pt, text 1.5pt lower

So a rule between two rows takes half its width from each, and the rules above and below the table take their whole width from their row. Between two rows ruled differently, Word makes room for the lower row's rule: a 1.5pt header over 0.5pt rows stepped as 0.5pt rules do, and a 1.5pt row under 0.5pt ones as 1.5pt rules do.

A table that states no rule was left on Word's own grid. That grid is thinner than the engine's default 1pt black rule the page draws, and gives its rows other heights.

What changed

• clearOfTheRules. A table cell's padding gives up, above and below, the room Word makes for the rules there. That is half the rule between two rows (the lower row's where the two differ), and the whole rule above the first row and below the last. In a table ruled alike throughout, with padding enough, every row then steps and stands as the page sets it. A padding thinner than its share gives what it has, and its row stands that much taller. The sides keep their padding, as the columns' widths are fixed.
• resolveCellStroke / ENGINE_DEFAULT_CELL_STROKE. A table that states no rule is written with the engine's default 1pt black rule, as resolveCellPadding and the cell fill already fall back to the engine's defaults. This is a visible change for such tables: their rules in Word are now the page's weight.
• Docs. CHANGELOG.md, the tables row of docs/recipes/docx-export.md and the table-rows row of backend-capability-matrix.md are updated. The committed word-export-companion.docx preview is re-rendered, as its table is ruled.

Verification

• Full reactor gate: ./mvnw -B -ntp clean verify -pl :graph-compose-core,:graph-compose-render-pdf,:graph-compose-render-docx,:graph-compose-render-pptx,:graph-compose-templates,:graph-compose-testing,:graph-compose-qa,:graph-compose-coverage -am gives BUILD SUCCESS (1791 + 127 tests). After install, examples are green (93 tests, with the refreshed preview), and the knowledge checks and extract-api --check pass.

• DocxCellPaddingTest:

  • A two-row 1.5pt-ruled table is written 110/125 and 125/110 twips above and below, with the sides untouched.
  • A table stating no rule gets the 1pt single rule, pinned to TableCellLayoutStyle.DEFAULT.
  • The padding tests now include the default rule's share. New cases: a 1.5pt header over 0.5pt rows gives the body's half at the edge; a cell spanning to the last row gives up the rule below the table whole; a zero-width rule gives up nothing; a padding thinner than its share goes to 0. Each rule of the model, when removed, fails its own test.

• DocxComposedCellTest: the row-height hold subtracts the margins as now written.

• Template corpus (62 documents), converted to PDF by Word, baselines matched by text:

  	median drift	lines > 2pt off
  all 62 (3614 lines), before → after	0.94 → 0.56pt	1341 → 858
  NorthlineProposal	0.8 → 0.4pt	50 → 7
  InvoiceClassic long	6.9 → 0.5pt	123 → 3
  InvoiceModern long	6.9 → 0.4pt	119 → 2

  • EditorialProposal is 2 pages in Word again; it was 3. In LibreOffice the corpus median falls from 1.59pt to 0.55.
  • Two other rule models were measured over the same corpus: half a rule off each side reached 0.60pt, and a whole rule below every row 0.74pt.
  • InvoiceWorkspace's median rises from 3.8 to 4.8pt. Its table now stands level; its rows had been growing by as much as its bill-to block runs 10pt high, and that block is a separate defect.

• Word on screen: a capture of Word's window shows NorthlineProposal's investment, terms and acceptance headings level with their badges, and EditorialProposal on two pages.

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