Add comprehensive memory accounting, string interning, and targeted optimizations across all browser subsystems: - New `memory` crate: MemoryReport/SubsystemStats for profiling, Atom (Rc<str>-backed interned strings), CompactString (22-byte SSO), typed Arena<T> bump allocator - DOM: tag names and attribute names now use Atom for deduplication, reducing per-element memory by ~7x for repeated tags; memory_usage() and element/text node counting methods added - Style: font_family uses Atom instead of String (saves 16 bytes per ComputedStyle); StyleCache gains len/is_empty/memory_usage methods; ComputedStyle.heap_bytes() for dynamic field accounting - Layout: LayoutTree gains box_count(), memory_usage(), LayoutHints for pre-allocation across frames - Render: display list compaction via build_display_list_into() that reuses buffer capacity; LayerTree.memory_usage() and utilization tracking for glyph atlas - JS GC: adaptive threshold (1.5x growth factor, capped at 1M), heap compaction when free ratio exceeds 50%, memory_usage() method - Net: HttpClient.memory_usage(), pooled/h2 connection counts - Text: GlyphCache.memory_usage() for bitmap data tracking - Browser: memory_stats module aggregating all subsystem stats into a formatted MemoryReport for debug/about:memory display Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>