Add PagePreview orphan-badge parity with Card.tsx

[WilfordGrimley]

Summary

• PR Render orphan Drive-ID cards from text/XML import #393 gave orphan Drive-ID cards (a Drive file ID this catalog has never
  indexed, e.g. from a foreign order) a corner OrphanBadge on Card.tsx
  (the classic editor's card renderer), but recorded a known gap in
  docs/features/foreign-order-resilience.md: PagePreview.tsx — the
  /display unified sheet's own renderer — had no equivalent visual
  treatment, even though it already rendered the orphan's image correctly.
• Closes that gap: PagePreviewSlotContent gains an orphanLabel?: string
  prop; when set (and a resolved imageUrl is present), the slot renders a
  data-testid="orphan-badge" pill in its top-right corner, matching
  Card.tsx's badge styling but reimplemented in this component's own mm-unit
  idiom (so it stays legible after the sheet's outer transform: scale(),
  same reasoning as the component's existing screen-only border/radius).
  Wired from both callers that already resolve a CardDocument:
  DisplayPage.tsx (the /display sheet) and PDFGenerator.tsx's fast
  preview.
• Same orphan-badge testid Card.tsx already uses, by design, so a spec can
  target either surface uniformly — this was the actual blocker: a parity
  test on the parity-wave1 branch (ImportXML.spec.ts's orphan-cardback
  case) is red today because no orphan indicator exists anywhere on
  /display.
• docs/features/foreign-order-resilience.md updated in place to mark the
  gap CLOSED, with the new files/props/tests recorded.

Why now

Foreign-order resilience is a high-priority feature (owner ruling,
2026-07-22/23) and /display is its acceptance surface. The badge gap was a
recorded, tracked item blocking a parity test elsewhere — this closes it on
master so that test's adaptation can proceed independently.

Evidence

• npx jest — 568/568 passing (64 suites), including new PagePreview.test.tsx
  "orphan badge" cases (label shown/omitted/gated on a resolved imageUrl).
• npx tsc --noEmit — clean.
• npx prettier@2.7.1 --check on every changed file — clean.
• npx playwright test tests/OrphanRendering.spec.ts (extended with sheet
  badge assertions on both faces + a new 390px-narrow case) — 3/3 passing.
• npx playwright test tests/PagePreview.spec.ts — 3/3 passing (no
  regression).
• npx playwright test tests/DisplayPage.spec.ts — 31/31 passing (no
  regression).
• Screenshots (zoomed crops confirm the "YOUR FILE" pill renders correctly):
  frontend/test-results/orphan-text-import-desktop.png,
  frontend/test-results/orphan-xml-import-desktop.png,
  frontend/test-results/orphan-xml-import-backs-desktop.png (the "cardback
  corner" case),
  frontend/test-results/orphan-text-import-narrow-390.png (390px phone
  viewport).

Test plan

• npx jest (full suite)
• npx tsc --noEmit
• npx prettier@2.7.1 --check on changed files
• npx playwright test tests/OrphanRendering.spec.ts (desktop + narrow)
• npx playwright test tests/PagePreview.spec.ts
• npx playwright test tests/DisplayPage.spec.ts
• wiki: no admin/user-facing docs page beyond docs/ itself covers this
  surface today — no wiki page identified as needing a change; flagging
  here per the merge-time checklist convention in case a reviewer knows
  of one this misses.

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