feat: comprehensive code block CSS

- Borderless container with subtle shadow
- VS Code filename header with dot indicators
- Line numbers via CSS counter
- Copy button (hover-visible)
- Highlighted line accent stripe
- Highlighted chars background
- Shiki dual theme token color switching
- Light and dark mode overrides for all code elements

app/globals.css

@@ -123,6 +123,131 @@
   --shadow-card: 0 1px 4px oklch(1 0 0 / 0.06);
 }
 
+/* === Code Blocks: Borderless, VS Code Style, Line Numbers === */
+[data-rehype-pretty-code-figure] {
+  @apply relative overflow-hidden rounded-[var(--radius-code)];
+  background-color: var(--color-code-block);
+  border: none;
+  box-shadow: 0 0 0 1px var(--color-border),
+              0 2px 8px oklch(0 0 0 / 0.06);
+}
+.dark [data-rehype-pretty-code-figure] {
+  box-shadow: 0 0 0 1px var(--color-border),
+              0 2px 8px oklch(1 0 0 / 0.04);
+}
+
+[data-rehype-pretty-code-title] {
+  @apply relative flex items-center gap-2.5 px-4 py-2 text-xs;
+  background-color: var(--color-code-title-bg);
+  border-bottom: 1px solid var(--color-border);
+  border-radius: var(--radius-code) var(--radius-code) 0 0;
+}
+.dark [data-rehype-pretty-code-title] {
+  background-color: var(--color-code-title-bg);
+}
+
+[data-rehype-pretty-code-title] + pre {
+  @apply m-0 rounded-b-[var(--radius-code)] rounded-t-none;
+}
+
+[data-rehype-pretty-code-title] .vscode-dots {
+  @apply inline-flex gap-[6px] mr-2;
+}
+[data-rehype-pretty-code-title] .vscode-dots span {
+  @apply block h-2.5 w-2.5 rounded-full;
+}
+[data-rehype-pretty-code-title] .dot-red {
+  background-color: var(--color-code-dot-red);
+  box-shadow: inset 0 0 0 0.5px oklch(0 0 0 / 0.15);
+}
+[data-rehype-pretty-code-title] .dot-yellow {
+  background-color: var(--color-code-dot-yellow);
+  box-shadow: inset 0 0 0 0.5px oklch(0 0 0 / 0.15);
+}
+[data-rehype-pretty-code-title] .dot-green {
+  background-color: var(--color-code-dot-green);
+  box-shadow: inset 0 0 0 0.5px oklch(0 0 0 / 0.15);
+}
+
+[data-rehype-pretty-code-figure] pre {
+  @apply relative overflow-auto p-4;
+}
+
+[data-rehype-pretty-code-figure] pre code {
+  @apply !bg-transparent font-mono text-[13px] leading-[1.6];
+  display: grid;
+}
+
+[data-rehype-pretty-code-figure] code[data-line-numbers] {
+  counter-reset: line;
+}
+[data-rehype-pretty-code-figure] code[data-line-numbers] > [data-line]::before {
+  counter-increment: line;
+  content: counter(line);
+  @apply mr-5 inline-block w-4 text-right select-none;
+  color: var(--color-code-gutter);
+  @apply text-[11px] font-mono;
+}
+.dark [data-rehype-pretty-code-figure] code[data-line-numbers] > [data-line]::before {
+  color: var(--color-code-gutter);
+}
+
+[data-rehype-pretty-code-figure] [data-line] {
+  @apply relative px-2;
+  border-left: 2px solid transparent;
+}
+
+[data-rehype-pretty-code-figure] [data-highlighted-line] {
+  @apply rounded-r-sm;
+  background-color: var(--color-code-line-highlight);
+  border-left-color: var(--color-code-line-highlight-border);
+}
+
+[data-rehype-pretty-code-figure] [data-highlighted-chars] {
+  @apply rounded py-0.5 px-1;
+  background-color: var(--color-code-mark-bg);
+}
+
+[data-rehype-pretty-code-figure] .rehype-pretty-copy {
+  @apply absolute right-3 top-3 z-10 flex items-center gap-1 rounded-md border px-2 py-1 text-xs font-medium;
+  background-color: oklch(0.97 0 0 / 0.85);
+  color: var(--color-code-copy);
+  opacity: 0;
+  transition: opacity 0.15s ease;
+}
+.dark [data-rehype-pretty-code-figure] .rehype-pretty-copy {
+  background-color: oklch(0.10 0 0 / 0.85);
+  color: var(--color-code-copy);
+}
+[data-rehype-pretty-code-figure]:hover .rehype-pretty-copy {
+  opacity: 1;
+}
+[data-rehype-pretty-code-figure] .rehype-pretty-copy:hover {
+  @apply border-current;
+  background-color: oklch(0.95 0 0 / 0.95);
+  color: var(--color-code-copy-hover);
+}
+.dark [data-rehype-pretty-code-figure] .rehype-pretty-copy:hover {
+  background-color: oklch(0.15 0 0 / 0.95);
+}
+[data-rehype-pretty-code-figure] .rehype-pretty-copy.rehype-pretty-copied {
+  @apply border-green-500/50;
+  color: oklch(0.55 0.18 140);
+}
+.dark [data-rehype-pretty-code-figure] .rehype-pretty-copy.rehype-pretty-copied {
+  color: oklch(0.70 0.15 140);
+}
+
+/* Shiki dual theme token color switching */
+code[data-theme*=" "],
+code[data-theme*=" "] span {
+  color: var(--shiki-light);
+}
+html.dark code[data-theme*=" "],
+html.dark code[data-theme*=" "] span {
+  color: var(--shiki-dark);
+}
+
 /* === Blog typography === */
 @plugin "@tailwindcss/typography";