feat: v4.6.0 — AI assistant, collaboration, knowledge base, and 15 more features

- AI Assistant plugin: multi-provider chat (OpenAI/Anthropic/Ollama/LM Studio),
  summarize/improve/translate commands, proofread via ai:analyze; calls
  proxied through main so API keys stay out of the renderer
- Collaboration plugin: anchor-based comments in .comments/ sidecars with
  drift detection and F8 navigation
- Local knowledge base: [[wiki-links]] with click-to-create + Backlinks panel
- Crash recovery: debounced session snapshots with restore prompt on launch
- Version history: pre-save snapshots, History panel with restore/diff/delete
- Real PDF encryption: swap pdf-lib for @cantoo/pdf-lib (probe-driven UI)
- XLSX export (native workbooks via JSZip), ODT headers/footers + page size
- Offline KaTeX (bundled CSS+fonts), local-first PlantUML rendering
- Editor: vim mode toggle, snippet Tab-expansion, zen word-goal setter,
  writing heatmap, writing-studio panels wired with rail icons
- Quick Note global scratchpad (Ctrl+Alt+Q), markdownconverter:// deep links,
  REPL first-run confirmation
- Fix: Ctrl+Shift+P collision, pandoc converter availability check, CLI
  dangling --css/--reference-doc flags, dead converter button

8 new test suites; 613 tests green; lint clean

package.json

@@ -1,6 +1,6 @@
 {
   "name": "markdown-converter",
-  "version": "4.5.0",
+  "version": "4.6.0",
   "description": "Professional Markdown editor and universal file converter with PDF editing, batch processing, and syntax highlighting",
   "main": "src/main.js",
   "scripts": {
@@ -55,6 +55,7 @@
     "prettier": "^3.7.4"
   },
   "dependencies": {
+    "@cantoo/pdf-lib": "^2.9.1",
     "@codemirror/autocomplete": "^6.20.1",
     "@codemirror/commands": "^6.10.2",
     "@codemirror/lang-css": "^6.3.1",
@@ -69,6 +70,7 @@
     "@codemirror/state": "^6.5.4",
     "@codemirror/theme-one-dark": "^6.1.3",
     "@codemirror/view": "^6.39.16",
+    "@replit/codemirror-vim": "^6.4.0",
     "codemirror": "^6.0.2",
     "core-util-is": "^1.0.3",
     "docx": "^9.6.0",
@@ -79,11 +81,11 @@
     "highlight.js": "^11.11.1",
     "html2pdf.js": "^0.14.0",
     "jszip": "^3.10.1",
+    "katex": "^0.18.5",
     "marked": "^17.0.3",
     "marked-footnote": "^1.4.0",
     "marked-highlight": "^2.2.3",
     "mermaid": "^11.12.3",
-    "pdf-lib": "^1.17.1",
     "pdfjs-dist": "^5.5.207",
     "pdfkit": "^0.17.2",
     "pizzip": "^3.2.0",