fix(docx): hold a composed chip's row less the borders both editors draw outside it

[DemchaAV]

Why

CobaltRota's staff rows each stood up to 1.1pt taller in Word than on the page, and its last row 6.5pt low.

• A shape composed in a table cell (a chip) is written as a one-cell table. Its row is held at least the outline's height, less the cell's margins and the heavier border (holdRowAtLeast).
• Both editors draw a cell's top and bottom borders outside that height. A 9.2pt chip outlined with a 1.125pt border measured 10.3pt in Word and 10.2pt in LibreOffice.
• Every staff row holding a stacked outlined chip grew by that border.

What changed

• writePanelPiece. The borders drawn outside the row's height (bordersOutside) are now computed once, before the two branches that hold a panel's row, and the composed-outline branch takes them off as the placed-panel branch already did.
  • The amount is the part of the top border no space above took, plus the bottom border, less the heavier of the two, which holdRowAtLeast already takes off.
  • Where the padding holds the top border, nothing comes off.
• verticalMargins Javadoc. It now says the other border of a panel's own cell comes off in writePanelPiece, where its padding does not hold its top border.
• Docs. CHANGELOG.md, the composed-shape paragraph of docs/recipes/docx-export.md, and the composed-cell sentence of docs/architecture/backend-capability-matrix.md.

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).
  • render-docx runs 737 tests.
  • After install, examples run 93 green.
  • The knowledge checks pass.
• DocxComposedCellTest.anOutlinedChipHoldsItsRowLessBothBorders (new).
  • A 9.2pt chip with a 1.125pt border holds its row at 139 twips.
  • The same chip with no border holds it at its outline's 184.
  • Holding the outline's height as before fails it: 161.
• Template corpus (62 documents), against 2.5-dev: only CobaltRota changes. It stays one page.
  • Word: p90 drift 6.41pt → 2.91, lines more than 2pt off 42 → 37. Its last staff row stands 2.35pt low instead of 6.55.
  • LibreOffice: p90 drift 7.26pt → 3.86.
  • An outlined chip now measures 9.48pt in Word against the page's 9.18. Its label's line, cut no deeper than its letters allow, sets the rest.

Known limits

• An outlined chip with padding at least as wide as its border is left as before. None in the templates was measured.
• A block after an outlined chip in the same cell is still drawn up by the chip's bottom border, as after a placed panel. Not drawing it up measured worse on a placed panel (ObsidianInvoice, Word median 0.25pt → 0.49), and no template places a block under a chip.
• Each staff row still stands 0.1–0.3pt taller than the page's. That comes from the hairline paragraphs closing each nested table, and is a separate change.

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