fix: override default light backgrounds for body, main, pre

Added explicit overrides for body, main, and pre elements to prevent
default light gray (#f7f7f7) backgrounds from showing through.

- Body and main: metal-bg-base (dark)
- Pre/code blocks: metal-bg-elevated (slightly lighter)
- Main container: metal-bg-surface with proper spacing

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

asciinema/theme/custom.css

@@ -36,9 +36,13 @@
   --pivoine-info: rgb(59, 130, 246);
 }
 
-/* Global Styling */
-body {
+/* Global Styling - Override default light backgrounds */
+body,
+main {
   background-color: var(--metal-bg-base) !important;
+}
+
+body {
   color: var(--metal-text-primary) !important;
   font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Roboto", "Helvetica Neue", Arial, sans-serif !important;
 }
@@ -201,11 +205,13 @@ article {
   padding-right: 15px !important;
 }
 
-/* Main container background */
+/* Main container - add surface background and padding */
 main .container {
   background-color: var(--metal-bg-surface) !important;
   padding: 24px !important;
   border-radius: 8px !important;
+  margin-top: 16px !important;
+  margin-bottom: 16px !important;
 }
 
 /* Forms & Inputs */
@@ -358,10 +364,11 @@ footer {
   margin-top: 48px;
 }
 
-/* Code Blocks */
+/* Code Blocks - Override default light background */
 pre,
-code {
-  background-color: var(--metal-bg-base) !important;
+code,
+pre code {
+  background-color: var(--metal-bg-elevated) !important;
   color: var(--metal-text-primary) !important;
   border: 1px solid var(--metal-border) !important;
   border-radius: 6px !important;