release: stamp v0.51.613 (#4800 streaming render freeze fix)

CHANGELOG.md

@@ -3,6 +3,12 @@
 
 ## [Unreleased]
 
+## [v0.51.613] — 2026-06-23 — Release VT (eliminate O(DOM) streaming render freeze on long answers)
+
+### Fixed
+
+- **Long agent answers no longer progressively freeze the UI while streaming.** On answers of 30,000+ characters (5,000+ DOM nodes), every streamed token ran a full-DOM link-sanitization scan, so render cost grew with the answer size and the tab eventually froze (and could crash the renderer). Link URL-scheme validation now happens inline as each DOM node is created (via a wrapped streaming-markdown renderer), eliminating the per-token full-DOM rescan, and the streaming render now caches its parse result to skip redundant re-parsing. Dangerous URL schemes (`javascript:`, `data:`, `vbscript:`, etc.) are still rejected on links and images exactly as before, and the final settled render still runs the full sanitizer. Thanks @wlknight. (#4800)
+
 ## [v0.51.612] — 2026-06-23 — Release VS (background-tab notifications + profile default workspace on fresh sessions)
 
 ### Fixed