Fence-aware preprocessor that converts `:::` container directives and standalone HTML comments into sentinel paragraphs before markdown-it parsing. Uses private-use Unicode characters as sentinels to avoid collision with author text. Respects CommonMark fence rules so `:::` inside code blocks stays literal — essential for graceful degradation. Also drops full-line HTML comments (`<!-- ... -->`) while leaving inline and multi-line comments untouched. This module is isolated (no internal imports beyond string utilities) and could be reused in any project needing to extend Markdown with directive syntax.

Parses info strings from fenced code blocks (e.g., `chart type=bar x=region y=sales`). Handles `key=value` pairs, bare flags, and quoted values with spaces. Returns a clean object with lang and opts. No external dependencies, entirely self-contained. Could be extracted for any application needing a simple, robust info-string parser without JSON or expressions.

Collection of utility functions for SVG chart rendering: niceTicks (generates 'nice' axis tick values), numericColumn (extracts and validates numeric data from rows, returning an error string for non-numeric values), formatNumber (formats numbers as currency, percent, thousands, or plain), escapeHtml, columnSet, and fmt. All functions are pure, isolated, and well-tested. Demonstrates good engineering for chart axis scaling and data validation. Could be reused in any charting or data visualization project.

Data loading and parsing module handling inline CSV/TSV/JSON and file-referenced datasets. CSV parser handles quoted fields, ragged rows (with configurable warning limits), and proper delimiter support. The `loadDataset` function enforces path security by resolving relative to a base directory and rejecting any path that escapes it — error messages report the author's relative path, never an absolute path. Includes JSON validation (must be array of objects). This module is self-contained and demonstrates both data engineering and security awareness.