docs(sdk-flow): add Realtime Validation shot to capture pipeline

[fuhrysteve]

Summary

Add a realtime-validation shot to the SDK capture pipeline + swap
the previously-broken <img> ref in docs/sdk-flow.md to the
captured S3 URL.

Image:
https://tpastream-public.s3.amazonaws.com/sdk-docs/flow-screenshots/realtime-validation.png

What the shot shows

The ActiveValidationsHero in its initial pending state
("Connecting… / Hang tight, this usually takes under a minute.")
right after a credential submit, with the choose-payer view
underneath ("Add another carrier") so the user can keep adding
carriers in parallel — exactly the UX the surrounding doc paragraph
describes.

How the capture works

scripts/screenshots/capture.mjs already supports real-token init
(used by error-init-page and select-enroll-widget). The new
shot reuses that, drives through SelectEnrollProcess →
choose-payer → credentials form → submit, then waits on the hero
"Connecting…" text before clipping.

Two mocks make the shot deterministic:

• POST /sdk-api/policy_holder_sdk/policy_holder is stubbed to
  return a fake task_id / task_token immediately — no real
  backend validation gets queued.
• GET /v3/sdk/progress/<task_id>/stream hangs for 45 s so the
  hero stays in pending instead of transitioning to
  pending_async (clean SSE close) or failure (abort/error).

The corner ActiveValidationsPanel duplicates the hero copy and
visually overlaps it at the typical 560-px embed width, so it's
hidden via addStyleTag right before the capture for legibility.

What changed in capture.mjs

• captureOne now accepts either a fulfill object (the common
  case) or an async handler function for routes[i][1] — the
  handler form is what the new shot uses to stall the SSE.
• SDK_SHOTS_DEBUG=1 env flag wires up pageerror +
  console.error logging during iteration; off by default to keep
  capture runs quiet.
• New realtime-validation entry in the SHOTS table.

Test plan

• Reviewer reads through scripts/screenshots/capture.mjs's
  new shot entry; the routes + drive are self-contained.
• After merge, deployed preview shows the new image under
  "Realtime Validation" on
  https://developers.tpastream.com/sdk/sdk-flow.

[Copilot]

Pull request overview

Adds a new realtime validation screenshot capture path and updates the SDK flow documentation to reference the hosted image.

Changes:

• Adds a realtime-validation screenshot scenario with credential-submit and SSE mocks.
• Extends screenshot routing to support async route handlers.
• Updates docs/sdk-flow.md to use the captured S3 image URL.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
scripts/screenshots/capture.mjs	Adds the realtime-validation shot, debug logging, and async route handler support.
docs/sdk-flow.md	Replaces the realtime validation image reference with the hosted S3 screenshot URL.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.