fix(docx): count a table's rules as both editors do, and round a cell and the chip composed in it once

[DemchaAV]

Why

A table's rows in Word and LibreOffice were held a twip apart from the page's wherever a rule's
width, a cell's margins or a chip composed in a cell rounded to the twip, and the twips added up row
by row. Each was measured in isolation:

• A rule was counted to the nearest twip. A border of w:sz eighths of a point is 2.5 twips an
  eighth; ten-row tables ruled at three, five, six, seven and nine eighths stepped each row by its
  margins, its line and 7, 12, 15, 17 and 22 twips, in both editors alike to a tenth of a twip — the
  width rounded down (12.5 → 12, 17.5 → 17). Counted to the nearest, a row held by its height
  under a rule of an odd number of eighths stood a twip short of the page's.
• A rule between two rows was halved, and each half rounded with its margin, so an odd one came
  off a twip short: 15 twips as 7 and 7, every row of NorthlineProposal's and
  EditorialProposal's investment tables a twip taller in both editors.
• A cell's top and bottom margins were rounded apart: two of 32.69 twips came to 66, not 65.
• A shape composed in a table cell was rounded up inside a row that holds its own height.
  CobaltRota's stacked shift chips are 183.69 twips; each held at 184 and its label cut at 184,
  two in a day cell stood every row they were in a twip taller (row probes of the sheet's staff
  rows, fifteen copies each, Word = LibreOffice to 0.03 twip). And an outlined chip whose letters
  keep its label taller than its borders leave room for grows in Word by the rest: every staff row
  with a split shift in one stood 3 twips taller.

Counted to the nearest, the rule had hidden most of this: CobaltRota's single-shift rows came out
right only because the extra twip of each rule cancelled the extra twip of their margins, and its
header stood up to 0.4pt high above a grid that ran to 0.8pt low.

What changed

In DocxSemanticBackend:

• eighthsInTwips counts a rule as floor(sz × 2.5) twips — the count borderTwips (a row's
  held height, verticalMargins, outerRulesBeyondOne) and ruleTwips (clearOfTheRules) share.
• clearOfTheRules shares a rule between two rows in whole twips: the row above it gives up
  half rounded down, the row under it the rest; the rules above and below the table stay whole to
  their row. outerRulesBeyondOne holds the first and last rows' extra rule twips to that same
  split (a first row its share of the rule under it, a last row the rest of the rule above it), so
  a held row's height and its margins agree to the twip.
• applyCellPadding rounds a cell's top and bottom margins together: the top to the nearest,
  the bottom to what the two come to less it. Panels' cells take the same path.
• A shape composed in a table cell (no placement of its own) is held at its outline's height
  rounded down (holdThePanelsHeight(…, inACell) → holdRowAtLeast(…, down) → twipsDown), and
  cutTheLabelToItsOutline cuts its label to the room rounded down: the row the cell is in holds
  the page's height rounded once, and anything in it rounded up grows it. A shape in the flow keeps
  rounding to the nearest.
• giveBackWhatTheLabelNeeds: where a cut label is still taller than the height its shape's row
  holds — an outlined chip whose letters stop the cut — that much comes out of the margins of the
  cell the shape is in, half above (rounded down) and half below, as far as they hold. The chip
  stays centred where the page centres it and the row keeps the page's height. Only where the shape
  is all its cell holds and the cell all its row holds (aloneInItsRow, set by writeCellNodes):
  what stands above the shape in its cell would move up with the top margin, and both editors give
  every cell of a row the row's largest margins, so beside another cell it gives nothing back.

Docs: CHANGELOG.md (v2.5.0), the recipe's Tables row and composed-shape paragraph, the backend
capability matrix's table and composed-shape rows.

Verification

• ./mvnw -B -ntp clean verify → BUILD SUCCESS: render-docx 1359 run, 0 failures, 1 skipped
  (+9), qa 1820, examples 93, core 818; with the odd-twip test added after it, render-docx
  1360 run, 0 failures.
• New tests: DocxCellPaddingTest — a 0.625pt and a 0.875pt rule come off at 12 and 17 twips; a
  0.7pt rule between two rows comes off as 7 above it and 8 below it; 1.6345pt margins are written
  33 and 32. DocxRuledRowHeightTest — every row of three-row tables ruled at five, six and seven
  eighths is held at its content's height, and a table's own unpadded, unruled row at five sizes
  at its line, both rounded to the nearest. DocxComposedCellTest — a 9.1846pt chip is held and its
  label cut at 183 twips; an outlined chip whose letters keep its label 20 twips past its row's 140
  leaves the cell it is all of 10 twips less above and below, a filled one nothing, a cell of 5
  twips nothing below zero, a chip beside another cell nothing at all, and 17 twips are given back
  8 above and 9 below. Changed:
  DocxRuleRowTest (a 0.9pt border counts 17 twips, the last row's share of the rule above it 9),
  DocxPanelTailTest (a 1.1pt panel border counts 22).
• Fourteen sabotages, each caught by its own test: the rule to the nearest; the lower row's share
  floored; the upper row's ceiled; the margins rounded apart; the first row's share ceiled; the last
  row's floored; the chip held to the nearest; the label cut to the nearest; no give-back; the
  give-back above only; a give-back beside another cell; every held row rounded down; the give-back
  past the margins; the odd twip given back above.
• Probe (export of tables of one, two, three and six rows ruled at five, six, seven and nine eighths
  between two lines, Lato 10pt, 4pt padding): every table takes the page's height to within ±0.8 twip
  in Word (its 2.4-twip grid) and to the twip in LibreOffice.
• DOCX fidelity corpus against 2.5-dev, Word (word-windows*.tsv): 10 documents nearer, 7
  further, the sum of the medians 0.16pt nearer — proposal-northline's p90 0.71 → 0.43pt,
  proposal-editorial's 1.20 → 0.81pt, cv-panel's median 0.43 → 0.31pt, invoice-subscription's
  0.43 → 0.33pt. LibreOffice on Windows (libreoffice-windows*.tsv): 10 nearer, 7 further —
  proposal-northline 0.27 → 0.17pt, cv-panel 0.39 → 0.26pt, invoice-subscription 0.34 → 0.24pt.
  LibreOffice on Linux (CI's docx-fidelity job, libreoffice-linux*.tsv, rewritten from its
  artifact on this branch in its own commit): against its measurement of 2.5-dev, 11 nearer, 5
  further, the sum of the medians 0.36pt nearer — invoice-subscription 0.34 → 0.19pt,
  invoice-platform 0.42 → 0.32pt, proposal-northline 0.27 → 0.17pt. The report is unchanged: the same 969 notes.

Notes for review

• CobaltRota's grid now stands where the page sets it: every rule under the table's top within a
  quarter point of the page's in Word, where they ran from 0.4pt high to 0.8pt low; its p90 0.99 →
  0.46pt in Word and 0.84 → 0.39pt in LibreOffice. Its median moves 0.32 → 0.38pt (0.23 → 0.31pt):
  the shifts' labels stand about 0.3pt low in their chips, a composed cell's first line not being
  seated, which the grid standing high had hidden. That seat is its own change.
• The other documents further are a twip or a step of Word's 0.12pt grid off where their tables and
  panels now take the page's height, and the lines after them show what they had hidden:
  invoice-classic's notes 0.2pt low under its totals table (which had stood 0.13pt high), where
  both editors leave more space after a table than the page does; invoice-platform's line items,
  already 0.3pt high in their cells, a twip higher with their rows where the page draws them (its
  rules within 0.11pt of the page's in LibreOffice); letter-panel's body, already 0.25pt high, a
  twip higher under its panel; the line items of invoice-consulting and its long version,
  invoice-metered and invoice-payments a step of the grid, or two to three twips. proposal-editorial in LibreOffice (44.46 → 44.75pt) is the
  document LibreOffice sets on a new page.
• On Linux, rota-cobalt's median moves nearer (0.23 → 0.17pt) and its p90 further (0.79 → 0.90pt):
  its grid no longer runs 0.8pt low, and the stacked chips' labels, which LibreOffice on Linux sets
  about 0.7pt high in their chips (its face substitutions), stand 1pt high. The job held 22 of its
  lines further against the baseline from before fix(docx): stand a table's text cells on the page's baselines, through their row's margins #876, with 5 of proposal-editorial's.
• The chip's own height in Word is still what its letters need: the give-back keeps the row, not
  the chip, at the page's height.
• A shape's own borders are still taken off at their authored width where it is held whole (the
  lighter of the two) and where its label's room is read: a panel's rule widths are their own change.
  At CobaltRota's 1.1pt outline the two counts agree to the twip.

Lane: shared-engine (DOCX backend) — render-docx only, no public API.