feat: 8 AI providers, rich text editor, agent notifications, UI contrast & font settings

- Add DeepSeek, OpenRouter, Mistral, Z.AI, LM Studio as AI providers
  with editable model names via Combobox in admin settings
- Fix OpenRouter broken by normalizeProvider bug in config.ts
- Convert agent-created notes from Markdown to HTML (TipTap rich text)
- Add Notification model + in-app notifications for agent results
- Agent notification click opens the created note directly
- Add note count display on notebook and inbox headers
- Fix checklist toggle in card view (persist state via localCheckItems)
- Add checklist creation option in tabs/list view (dropdown on + button)
- Fix image description ENOENT error with HTTP fallback
- Improve UI contrast across all themes (input, border, checkbox visibility)
- Add font family setting (Inter vs System Default) in Appearance settings
- Fix CSS font-sans variable conflict (removed dead Geist references)
- Update README with new features and 8 providers

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

memento-note/components/note-inline-editor.tsx

@@ -497,8 +497,14 @@ export function NoteInlineEditor({
             value={noteType}
             onChange={(newType) => {
               setNoteType(newType)
-              if (newType !== 'markdown') setShowMarkdownPreview(false)
-              onChange?.(note.id, { isMarkdown: newType === 'markdown' })
+              if (newType === 'markdown') setShowMarkdownPreview(true)
+              else setShowMarkdownPreview(false)
+              // Persist both type and isMarkdown immediately
+              saveInline(note.id, {
+                type: newType,
+                isMarkdown: newType === 'markdown',
+              }).catch(() => {})
+              onChange?.(note.id, { type: newType, isMarkdown: newType === 'markdown' })
             }}
             compact
           />