Major update for v1 and tests

fonts/README.md

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+# Server-side font files
+
+This directory is scanned by `server.js` at startup. Each `.ttf` or `.otf` file
+is registered with node-canvas via `registerFont()` so that exports render
+text in the same fonts the editor previews.
+
+## Filename convention
+
+```
+<Family_Name>-<Variant>.ttf
+```
+
+- Spaces in family names become underscores in the filename so the file is
+  portable across operating systems. The server replaces them back to spaces
+  at registration time.
+- The variant is parsed for the substrings `Bold` and `Italic` to set the
+  `weight` and `style` registration options. `Regular` (or anything else) is
+  treated as the default weight.
+
+Examples:
+| File | Family | Weight | Style |
+|---|---|---|---|
+| `Roboto-Regular.ttf` | Roboto | normal | normal |
+| `Roboto-Bold.ttf` | Roboto | bold | normal |
+| `DM_Sans-Regular.ttf` | DM Sans | normal | normal |
+| `Open_Sans-BoldItalic.ttf` | Open Sans | bold | italic |
+
+## Populating this directory
+
+```
+npm run fetch-fonts
+```
+
+This downloads TTFs for the editor's font list from the Fontsource jsDelivr
+CDN. Re-running is a no-op for already-present files; pass `--force` to
+re-download.
+
+## What if I leave it empty?
+
+The server still starts and exports still work, but every text element will
+render in whatever fallback font the host system happens to have for the
+requested family. On a stock Alpine container that's a generic sans-serif. On
+macOS dev machines, system-installed fonts usually fill in for the common
+names but not the more specialized ones.