chore: track .impeccable/live/config.json for this repo

Live mode injection config for the Astro site (Base.astro, before </body>,
HTML comment syntax). The .gitignore already permits tracking generated
sidecars; this commit makes the choice explicit so contributors get the
same wiring on first run.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.impeccable/live/config.json

@@ -0,0 +1,6 @@
+{
+  "files": ["site/layouts/Base.astro"],
+  "insertBefore": "</body>",
+  "commentSyntax": "html",
+  "cspChecked": true
+}