feat: implement PostHog event tracking plan

Add trackEvent() calls for all user actions in the tracking plan:
- Vault: vault_opened (with has_git, note_count), vault_switched
- Notes: note_created (with has_type, creation_path), note_deleted,
  note_trashed, note_archived, note_favorited, note_unfavorited
- Git: commit_made, sync_triggered
- Search: search_used
- Editor: raw_mode_toggled, wikilink_inserted
- Types & Views: type_created, view_created
- Telemetry: telemetry_opted_in, telemetry_opted_out

All events gated by PostHog initialization (only fires when opted in).
No PII in any event properties — counts, booleans, and enums only.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/RawEditorView.tsx

@@ -1,4 +1,5 @@
 import { useRef, useState, useCallback, useEffect, useMemo } from 'react'
+import { trackEvent } from '../lib/telemetry'
 import type { EditorView } from '@codemirror/view'
 import { preFilterWikilinks, deduplicateByPath, MIN_QUERY_LENGTH } from '../utils/wikilinkSuggestions'
 import { attachClickHandlers, enrichSuggestionItems } from '../utils/suggestionEnrichment'
@@ -136,6 +137,7 @@ export function RawEditorView({ content, path, entries, onContentChange, onSave,
       changes: { from: 0, to: doc.length, insert: newText },
       selection: { anchor: newCursor },
     })
+    trackEvent('wikilink_inserted')
     setAutocomplete(null)
 
     if (debounceRef.current) clearTimeout(debounceRef.current)

src/components/SettingsPanel.tsx

@@ -2,6 +2,7 @@ import { useState, useRef, useCallback, useEffect } from 'react'
 import { X, Eye, EyeSlash, GithubLogo, SignOut } from '@phosphor-icons/react'
 import { GitHubDeviceFlow } from './GitHubDeviceFlow'
 import type { Settings } from '../types'
+import { trackEvent } from '../lib/telemetry'
 
 interface SettingsPanelProps {
   open: boolean
@@ -152,6 +153,10 @@ function SettingsPanelInner({ settings, onSave, onClose }: Omit<SettingsPanelPro
   }), [openaiKey, googleKey, githubToken, githubUsername, pullInterval, updateChannel, crashReporting, analytics, settings.telemetry_consent, settings.anonymous_id])
 
   const handleSave = () => {
+    const prevAnalytics = settings.analytics_enabled ?? false
+    const newAnalytics = analytics
+    if (!prevAnalytics && newAnalytics) trackEvent('telemetry_opted_in')
+    if (prevAnalytics && !newAnalytics) trackEvent('telemetry_opted_out')
     onSave(buildSettings())
     onClose()
   }

src/components/SingleEditorView.tsx

@@ -1,4 +1,5 @@
 import { useEffect, useCallback, useMemo, useRef } from 'react'
+import { trackEvent } from '../lib/telemetry'
 import { useCreateBlockNote, SuggestionMenuController } from '@blocknote/react'
 import { BlockNoteView } from '@blocknote/mantine'
 import { useEditorTheme } from '../hooks/useTheme'
@@ -87,6 +88,7 @@ export function SingleEditorView({ editor, entries, onNavigateWikilink, onChange
       { type: 'wikilink' as const, props: { target } },
       " ",
     ])
+    trackEvent('wikilink_inserted')
   }, [editor])
 
   const getWikilinkItems = useCallback(async (query: string): Promise<WikilinkSuggestionItem[]> => {