- New markdown-it content script intercepts ```gtd-calendar fences and
emits a placeholder div (config URI-encoded in a data attribute)
- New webview asset (gtd-calendar-webview.js) finds placeholders, requests
data via webviewApi.postMessage, renders a debug view, and wires
click-to-open drilldown (openNote command)
- index.ts registers the content script and handles getEvents/openNote;
getEvents parses the YAML config for real but returns hardcoded events,
including one pointing at the current note to prove drilldown
- Old event-calendar content script removed; Calendar/ classes retained
for reuse in Phase 3
- Fork CSS section appended (placeholder, error, debug styles)
