feat: enhance OG/Twitter meta tags with cover images

- Use page resource cover.* for track pages (resized to 1200x webp)
- Fall back to .Params.image then configurable site default
- Add [images] config section with default OG image path
- Add og-default.png (1200x630) with centered logo

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

config/_default/params.toml

@@ -14,3 +14,6 @@ email = "valknar@pivoine.art"
 [visualizer]
   particleCount = 5000
   fftSize = 512
+
+[images]
+  default = "/images/og-default.png"

layouts/partials/head/opengraph.html

@@ -1,7 +1,19 @@
 {{- $title := .Title | default .Site.Title -}}
 {{- $desc := .Description | default .Summary | default .Site.Params.description | plainify | truncate 200 -}}
-{{- $image := .Params.image | default "/images/og-default.png" -}}
+
-{{- if not (strings.HasPrefix $image "http") -}}
+{{/* Resolve image: page resource cover.* > .Params.image > site default */}}
+{{- $image := "" -}}
+{{- with .Resources.GetMatch "cover.*" -}}
+  {{- $img := .Resize "1200x webp q90" -}}
+  {{- $image = $img.Permalink -}}
+{{- else -}}
+  {{- with $.Params.image -}}
+    {{- $image = . -}}
+  {{- else -}}
+    {{- $image = $.Site.Params.images.default | default "/images/og-default.png" -}}
+  {{- end -}}
+{{- end -}}
+{{- if and $image (not (strings.HasPrefix $image "http")) -}}
   {{- $image = $image | absURL -}}
 {{- end -}}
 

layouts/partials/head/twitter.html

@@ -1,11 +1,23 @@
 {{- $title := .Title | default .Site.Title -}}
 {{- $desc := .Description | default .Summary | default .Site.Params.description | plainify | truncate 200 -}}
-{{- $image := .Params.image | default "/images/og-default.png" -}}
+
-{{- if not (strings.HasPrefix $image "http") -}}
+{{/* Resolve image: page resource cover.* > .Params.image > site default */}}
+{{- $image := "" -}}
+{{- with .Resources.GetMatch "cover.*" -}}
+  {{- $img := .Resize "1200x webp q90" -}}
+  {{- $image = $img.Permalink -}}
+{{- else -}}
+  {{- with $.Params.image -}}
+    {{- $image = . -}}
+  {{- else -}}
+    {{- $image = $.Site.Params.images.default | default "/images/og-default.png" -}}
+  {{- end -}}
+{{- end -}}
+{{- if and $image (not (strings.HasPrefix $image "http")) -}}
   {{- $image = $image | absURL -}}
 {{- end -}}
 
-{{/* Determine card type */}}
+{{/* Determine card type - use large image when we have one */}}
 {{- $cardType := "summary" -}}
 {{- if $image -}}
   {{- $cardType = "summary_large_image" -}}