feat: ingest CSV and TSV as bounded documents

[skilfoy]

Summary

• add built-in CSV/TSV document ingestion with no new runtime dependency
• parse untrusted delimited data with strict, pre-validated resource bounds
• render contextualized Markdown sidecars with shape and truncation metadata
• make sidecar freshness content/version-aware and add CSV/TSV watch support

Closes #2119

Why

Research corpora commonly include experiment exports, survey tables, benchmark results, inventories, and market datasets in CSV/TSV form. Graphify previously left those files unclassified, so they never reached semantic extraction.

This implementation converts them into the same Markdown document path used by the existing extraction pipeline while preserving table context and keeping formulas inert.

Safety and behavior

The converter:

• supports UTF-8 and UTF-8-BOM;
• uses the standard-library csv parser with strict malformed-quote handling;
• validates every logical record before csv.reader materializes it;
• rejects logical records above 2 MiB or 1,000 parser columns;
• caps accepted input at 50 MiB, output at 1.1 million characters, rendered data at 1,000 rows × 100 columns, and fields at 10,000 characters;
• reports row/column/field/output truncation in sidecar metadata;
• escapes active Markdown/HTML constructs while preserving formulas and values as text;
• hashes source content plus a converter version in the sidecar marker, so same/older-mtime changes refresh correctly and unchanged inputs do not churn;
• keeps the Office converter unchanged to avoid coupling this feature to optional dependencies or ongoing Office-format work.

Tests

• pytest tests/test_delimited.py tests/test_detect.py tests/test_office_incremental.py tests/test_office_limits.py tests/test_watch.py -q
  • 312 passed
• pytest -q --ignore=tests/test_falkordb_integration.py
  • 3,628 passed, 1 skipped
• full pytest -q
  • all non-FalkorDB tests passed; the two live FalkorDB tests failed because a regular Redis instance occupied localhost:6379 and returned unknown command GRAPH.QUERY
• Python 3.10 focused matrix
  • 20 passed
• pyright graphify/delimited.py
  • 0 errors, 0 warnings
• Ruff and git diff --check
  • passed
• python -m build
  • sdist and wheel built successfully; graphify/delimited.py is packaged

An end-to-end temporary-corpus probe also verified detection, Markdown sidecar creation, untrusted-source prompt wrapping, formula preservation, quoted multiline values, unchanged-sidecar reuse, and content refresh with a preserved source mtime.

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