refactor: decompose NoteList into focused components and extract helpers

Break up NoteListInner (cc=61, 331 LoC, score 6.94) into:
- NoteItem: extracted item rendering component (score 9.63)
- SortDropdown: extracted into own file (score 9.68)
- noteListHelpers.ts: all utility functions (score 10.0)
  - GroupBuilder class replaces 5-arg addResolvedGroup
  - filterEntries split into filterByKind/filterByFilterType
- PinnedCard: unified entity/type document cards
- RelationshipGroupSection: extracted group rendering
- NoteList.tsx: orchestration only (score 8.79)

NoteListInner reduced from cc=61 to cc=23, 331 → 105 LoC.

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

src/hooks/useKeyboardNavigation.ts

@@ -1,6 +1,6 @@
 import { useEffect, useMemo, useRef } from 'react'
 import { isTauri } from '../mock-tauri'
-import { filterEntries, sortByModified, buildRelationshipGroups } from '../components/NoteList'
+import { filterEntries, sortByModified, buildRelationshipGroups } from '../utils/noteListHelpers'
 import type { VaultEntry, SidebarSelection } from '../types'
 
 interface Tab {