Add graph editor filter, anchor-based positioning, and context docs

- Add name/kind/subtype filter bar with keyboard shortcut (F key)
- Filtered-out nodes get dimmed styling, nearly invisible on minimap
- Add anchor-based positioning for minimap and toolbar (remembers
  which corner element is closest to, maintains offset on resize)
- Fix minimap not movable after reload (_applyMinimapAnchor undefined)
- Fix ResizeObserver to use anchor system for both minimap and toolbar
- Add graph-editor.md context file and update frontend.md with graph sync notes
- Add filter i18n keys for en/ru/zh locales

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

contexts/frontend.md

@@ -156,3 +156,9 @@ document.addEventListener('languageChanged', () => {
 ```
 
 Static HTML using `data-i18n` attributes is handled automatically by the i18n system. Only dynamically generated HTML needs this pattern.
+
+## Visual Graph Editor
+
+See [`contexts/graph-editor.md`](graph-editor.md) for full graph editor architecture and conventions.
+
+**IMPORTANT:** When adding or modifying entity types, subtypes, or connection fields, the graph editor files **must** be updated in sync. The graph maintains its own maps of entity colors, labels, icons, connection rules, and cache references. See the "Keeping the graph in sync with entity types" section in `graph-editor.md` for the complete checklist.