Adds the ocr.page.extract.chandra-ocr-2.v1 capability end to end: the
postOcrEscrow builder (locking the min-ada floor for the Submitted-state
datum, required since the min-ada fix), the gateway OCR route that selects
an OCR supplier by capability, posts a per-page escrow, calls the supplier,
verifies and settles, and returns content plus the signed receipt labelled
first-party-brokered. Supplier OCR handler with a hosted document-API
upstream and buyer-SDK OCR support included.
Squashed from the 2026-08-06 working subset; the deploy pack is
intentionally excluded (it lives in a private operator repo).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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