feat: add support for stat sheet SVG rendering

Introduces the ability to discover and render `*.sheet.svg` files.
These files can contain `<text>` elements with `${key}` templates
that reactively update based on the current journal stats.

- Add `StatSheet` type and CLI scanning logic
- Implement `SheetView` for rendering SVGs with live bindings
- Add `parseSheet` utility to extract template patterns from SVG
- Update file indexer to include `.svg` files

src/data-loader/file-index.ts

@@ -50,7 +50,7 @@ function ensureIndexLoaded(): Promise<void> {
       try {
         const context = import.meta.webpackContext("../../content", {
           recursive: true,
-          regExp: /\.md|\.yarn|\.csv$/i,
+          regExp: /\.md|\.yarn|\.csv|\.svg$/i,
         });
         const keys = context.keys();
         const index: FileIndex = {};
@@ -94,7 +94,7 @@ async function scanDirectory(
   prefix = "",
 ): Promise<FileIndex> {
   const index: FileIndex = {};
-  const acceptedExt = /\.(md|yarn|csv)$/i;
+  const acceptedExt = /\.(md|yarn|csv|svg)$/i;
 
   for await (const [name, entry] of (handle as any).entries()) {
     if (entry.kind === "directory") {