Resolve share URLs from the instance host and ship 1200×630 Open Graph images.

Staging no longer advertises production canonicals, and Slack/social previews get a default hero card with template and article overrides.

Co-authored-by: Cursor <cursoragent@cursor.com>

messages/en/metadata.json

@@ -2,6 +2,10 @@
   "_comment": "Page metadata. `title` is the page segment; the root layout template appends the site name. Home `title` is the full default document title (not passed through the template).",
   "siteName": "CommunityRule",
   "titleTemplate": "%s — CommunityRule",
+  "shareImage": {
+    "defaultAlt": "CommunityRule — build operating manuals for successful communities",
+    "templatesAlt": "CommunityRule governance templates"
+  },
   "home": {
     "title": "CommunityRule - Build operating manuals for successful communities",
     "description": "Help your community make important decisions in a way that reflects its unique values.",