fix(scroll): use hash navigation for marker clicks

Browser handles scroll natively via window.location.hash, respecting
scroll-margin-top. Updates URL for shareability and screen reader
compatibility. Added html { scroll-behavior: smooth } for smooth
hash navigation globally.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Vgmzx8VTTTmCskSpQtsLTr

themes/intotheeast/css/style.css

@@ -1,5 +1,7 @@
 *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
 
+html { scroll-behavior: smooth; }
+
 body {
     font-family: var(--font-ui);
     font-size: var(--text-base);