P0-10: Evaluate markdown-it-py for PTT and hypothesis parsing in shadow mode

[Dan-StrategicAutomation]

Backlog metadata

• Priority: P0
• Backlog order: P0-10
• Type: Research / refactor
• Area: PTT / hypothesis parsing
• Status: Open
• Depends on: P0-06: Consolidate shared guard results, CLI setup and review helpers #132
• Related work: Precedes P0-11: Migrate PTT and hypothesis updates to source-preserving Markdown patches #137

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Summary

From the 20 September 2026 Violin dev duplication/library review, baseline 5ca0d9d6767b91fe809b2e4996c85ac65ba9e962. Priority: P0. Source locations and measurements describe the review baseline.

Scope

Add a bounded markdown-it-py proof of concept with table support alongside existing core/ptt.py and core/hypotheses.py readers. Use heading/table/list tokens and source maps to extract typed domain records. Compare old and new records on sanitized engagement fixtures before switching any writes.

Acceptance criteria

• Cover escaped pipes, extra table columns, heading variations, comments, malformed records, prose and all protected template sections.
• Report every parser disagreement with source positions; document accepted grammar and resolution.
• Existing writer remains authoritative; no production dual-write or security-policy change.
• Declare/pin dependency appropriately only with demonstrated grammar support and maintenance benefit.

Dependencies / related work

Sequence after #132.

No existing open issue covers structural Markdown parser migration.

Verification

Working branch: codex/review-markdown-shadow, based on dev. Future PRs target dev; follow AGENTS.md and preserve fail-closed policy. Rebase dependent branches onto updated dev before implementation.

Implementation must pass uv run pytest, uv run ruff check ., uv run ruff format --check . and uv run python scripts/violin_guard.py check-release, plus the focused checks above. No implementation or test rerun is claimed by this tracking issue.