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

tests/ai-assistant-prompts.test.js

@@ -0,0 +1,84 @@
+/**
+ * AI Assistant prompt builder + proofread parser tests (pure module, jsdom
+ * not required but harmless under the default environment).
+ */
+const {
+  buildTaskPrompt,
+  buildProofreadPrompt,
+  parseProofreadIssues,
+} = require('../src/plugins/built-in/ai-assistant/prompts');
+
+describe('AI Assistant prompts', () => {
+  describe('buildTaskPrompt', () => {
+    it('builds a summarize prompt embedding the text', () => {
+      const { system, user } = buildTaskPrompt('summarize', 'the text here');
+      expect(system).toMatch(/summar/i);
+      expect(user).toContain('the text here');
+    });
+
+    it('passes the target language through for translate', () => {
+      const { user } = buildTaskPrompt('translate', 'bonjour', 'English');
+      expect(user).toContain('English');
+      expect(user).toContain('bonjour');
+    });
+
+    it('throws on unknown actions', () => {
+      expect(() => buildTaskPrompt('nope', 'x')).toThrow(/Unknown AI task/);
+    });
+
+    it('tolerates missing text', () => {
+      expect(buildTaskPrompt('explain', undefined).user).toBe('Explain the following:\n\n');
+    });
+  });
+
+  describe('buildProofreadPrompt', () => {
+    it('asks for a strict JSON array', () => {
+      const { system, user } = buildProofreadPrompt('Some text.');
+      expect(system).toMatch(/JSON array/);
+      expect(user).toContain('Some text.');
+    });
+  });
+
+  describe('parseProofreadIssues', () => {
+    it('parses a clean JSON array', () => {
+      const issues = parseProofreadIssues(
+        '[{"type":"Spelling","message":"teh","suggestion":"the"}]'
+      );
+      expect(issues).toEqual([{ type: 'spelling', message: 'teh', suggestion: 'the' }]);
+    });
+
+    it('strips code fences and surrounding prose', () => {
+      const issues = parseProofreadIssues(
+        'Here you go:\n```json\n[{"type":"grammar","message":"run on","suggestion":"split"}]\n```\nDone!'
+      );
+      expect(issues).toHaveLength(1);
+      expect(issues[0].suggestion).toBe('split');
+    });
+
+    it('tolerates trailing commas', () => {
+      const issues = parseProofreadIssues(
+        '[{"type":"style","message":"wordy","suggestion":"cut",},]'
+      );
+      expect(issues).toHaveLength(1);
+    });
+
+    it('returns [] for empty/garbage input instead of throwing', () => {
+      expect(parseProofreadIssues('')).toEqual([]);
+      expect(parseProofreadIssues('no json at all')).toEqual([]);
+      expect(parseProofreadIssues('{"not":"an array"}')).toEqual([]);
+      expect(parseProofreadIssues(null)).toEqual([]);
+    });
+
+    it('drops malformed entries and caps the list length', () => {
+      const many = Array.from({ length: 300 }, (_, i) => ({
+        type: 'grammar',
+        message: `m${i}`,
+        suggestion: 's',
+      }));
+      expect(parseProofreadIssues(JSON.stringify(many))).toHaveLength(100);
+      const mixed = parseProofreadIssues('[{"message":"ok","suggestion":"x"},null,42,{"foo":1}]');
+      // null/number entries dropped; {foo:1} dropped for lacking message+ suggestion
+      expect(mixed).toHaveLength(1);
+    });
+  });
+});