docs: capture pdf domain language and deferred ingestion backlog

Co-authored-by: Cursor <cursoragent@cursor.com>

backlog/persian-cloud-ocr.md

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+# Persian / cloud OCR
+
+## Why deferred
+
+Local OCR (e.g. Tesseract + `fas`/`fa`) may be good enough — or may destroy RTL, digits, and legal phrasing. Don’t commit to a vendor until measured.
+
+## Trigger
+
+Local OCR on a Farsi Scanned PDF sample set produces systematically bad characters, broken line order, or unusable tables.
+
+## Options to A/B
+
+| Option | Pros | Cons |
+|--------|------|------|
+| Tesseract + Persian models | Free, offline, no data leaving the box | Quality varies; tuning burden |
+| Cloud OCR (Google / Azure / etc.) | Often better on Persian print | Cost, latency, compliance |
+| Commercial Persian-focused OCR | Domain fit | Vendor lock-in |
+
+## Success criteria
+
+- Character error rate low enough that answer Faithfulness in Experiments doesn’t collapse vs Text PDF baseline
+- RTL paragraphs stay coherent in Chunk Preview