feat(templates): add the Workspace SaaS invoice preset

[DemchaAV]

Why

slack-invoice is the second bundle whose source carries a real company's identity, and
the second invoice built to paginate. It follows the pattern #638 set: the layout is
ported in full, the identity is not.

What

invoice.presets.WorkspaceInvoice on the existing StructuredInvoiceData model, on top
of the recipient registration added in #640.

De-branded

Two assets, both dropped:

• brand-lockup.svg was the real Slack wordmark (logos:slack) and
  item-brand-mark.svg its glyph, which the design draws bare on one service line while
  every other mark sits on a coloured tile. Neither is ported.
• The bare-mark rule survives without it: a packaged token that the design gives no
  tile colour is drawn bare, so the behaviour is general rather than tied to one mark.
• The other eight glyphs are stock Material icons; only their token names were
  product-flavoured (item-key-management, item-workflow, item-support), so they are
  renamed to what they draw: search, grid, shield.
• The legal entity, the product names and the closing words were always data. The
  shipped sample is neutral.

Money, the other way round

PaymentsInvoice carries a currency symbol on every figure. This design does the
opposite: it names the currency once per money column and writes the figures under it
bare, putting the code only on the total (USD 587.50). The preset follows its own
design rather than its sibling, and a quantity is written with what it counts
(50 Users) from the model's quantity and unit.

Two measured type corrections

A cap read off a screenshot includes about half a pixel of antialiasing on each edge and
the whole of it lands in the size, so sizeForCap takes it back off. And the body face
sets uppercase about 6% wider than the design's at the same cap height — measured across
three all-caps runs, while mixed-case runs at the same sizes matched within 2% — so
sizeForCaps carries that as a size correction. There is no letter-spacing API to take
it out with instead.

Tests

• Pixel parity against the bundle: 8 115 of 2 173 720 differing pixels, and the heat
  map has exactly two bands — x 45..256, y 46..99 (the lockup box, 7 285 px) and
  x 60..91, y 724..755 (a 31 × 31 square at the first line's mark, 830 px). Both are
  the marks deliberately not shipped. The accent bar, the issuer block, the metadata
  grid and its divider, both parties and their discs, all four table rows including the
  three tiled marks, the payment card, the totals, the accent rule, the due panel, the
  thank-you block and the closing band are pixel-identical; 207 layout nodes, and the
  text layer differs only by the wordmark.
• The bundle also freezes to 0 against its own published preview on both its pinned
  engine (2.2.2) and 2.2.3-SNAPSHOT, so there is no engine drift to account for.
• WorkspaceInvoiceSmokeTest — 16 cases: the packaged marks, the unknown-mark data
  error, a line with no mark, the wordmark fallback, the currency named once and not on
  every figure, the quantity with its unit, both parties' registrations and the absent
  one, the closing address as an annotation, a missing ship-to, a payment card with no
  note, an empty document, and a thirty-line invoice that runs on, repeats its column
  names on page two and numbers its pages.
• WorkspaceInvoiceLayoutSnapshotTest — exact geometry, one page.
• WorkspaceInvoiceVisualParityTest — pixel baseline; recorded without disturbing any
  other baseline in the suite.
• Full reactor gate green, and the examples suite (77 tests) run separately because the
  reactor gate does not cover it — the committed preview is rendered from a full
  install of this branch, so the catalogue's drift test passes.
• The showcase gains invoice-workspace-v2.