bf19e982fe
Adds a markdown-it extractor for ```tikz blocks that emits a sanitized placeholder, plus a runTikz() that lazy-loads the obsidian-tikzjax 0.5.2 bundle from jsdelivr on first encounter, sanitizes the produced SVG with DOMPurify, and caches it in PouchDB keyed by sha256(source) so repeat views are instant and offline-capable.