chore(layout): remove v2 nav-folding orphans surfaced by P4 refactor

P4 (Plan 2.5, AD-2.5-W1 + AD-2.5-B1) refactored SidebarNav to read
APP_NAVIGATION directly, retiring the OrganizerLayoutV2 → useV2Nav →
AppSidebar :groups → SidebarNav :groups props chain. Five artifacts
were deliberately left in place to keep the P4 diff focused — this
commit removes them.

Deleted:
- src/composables/useV2Nav.ts (+ spec) — v1→v2 nav fold adapter, no
  production consumer post-P4
- src/types/v2/nav.ts — V2NavGroup / V2NavItem types, only consumed
  by the deleted composables above. types/v2/ directory removed (empty)
- src/components-v2/layout/sidebarNavActive.ts (+ spec) — pure helper,
  SidebarNav now uses inlined active check against NavItem.routeName
- navFixture export + V2NavGroup import from stories/v2/_helpers.ts

Also: stale "useV2Nav(orgNavItems)" reference scrubbed from
OrganizerLayoutV2.vue docstring (the function no longer exists; the
comment now describes the retired plumbing generically).

Suite delta: 575 → 557 (−18 specs). The drop is correct — the removed
specs tested deleted dead code (sidebarNavActive: 8 specs, useV2Nav:
10 specs), not contract behaviour.

vue-tsc clean. Scoped ESLint clean (0 errors). Final re-grep on all
deleted symbols (useV2Nav, V2NavGroup, V2NavItem, sidebarNavActive,
navFixture) returns zero hits across apps/app/src/.

Per zero-compromise gap 5 (delete > adapt): orphans don't stay.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/app/src/components-v2/layout/__tests__/sidebarNavActive.spec.ts

@@ -1,46 +0,0 @@
-import { describe, expect, it } from 'vitest'
-import { isNavItemActive } from '@/components-v2/layout/sidebarNavActive'
-import type { V2NavItem } from '@/types/v2/nav'
-
-function makeItem(name: string): V2NavItem {
-  return { id: name, label: name, icon: 'tabler-home', to: { name } }
-}
-
-describe('isNavItemActive', () => {
-  it('returns true when the current route name exactly matches', () => {
-    expect(isNavItemActive(makeItem('dashboard'), 'dashboard')).toBe(true)
-  })
-
-  it('returns false when the current route name differs', () => {
-    expect(isNavItemActive(makeItem('dashboard'), 'events')).toBe(false)
-  })
-
-  it('returns false when currentRouteName is null', () => {
-    expect(isNavItemActive(makeItem('dashboard'), null)).toBe(false)
-  })
-
-  it('returns false when currentRouteName is undefined', () => {
-    expect(isNavItemActive(makeItem('dashboard'), undefined)).toBe(false)
-  })
-
-  it('returns true for nested routes: item name is a prefix of current route (dash-separated)', () => {
-    // e.g. item "organisation" should be active on route "organisation-settings"
-    expect(isNavItemActive(makeItem('organisation'), 'organisation-settings')).toBe(true)
-  })
-
-  it('does not match partial-word prefixes: "org" should NOT match "organisation-settings"', () => {
-    expect(isNavItemActive(makeItem('org'), 'organisation-settings')).toBe(false)
-  })
-
-  it('handles symbol route names: returns false (not string — no match)', () => {
-    const sym = Symbol('dashboard')
-
-    expect(isNavItemActive(makeItem('dashboard'), sym)).toBe(false)
-  })
-
-  it('item with to as { name: string } matches correctly', () => {
-    const item: V2NavItem = { id: 'events', label: 'Events', icon: 'tabler-calendar', to: { name: 'events' } }
-
-    expect(isNavItemActive(item, 'events')).toBe(true)
-  })
-})

apps/app/src/components-v2/layout/sidebarNavActive.ts

@@ -1,37 +0,0 @@
-import type { V2NavItem } from '@/types/v2/nav'
-
-/**
- * Pure helper — determines whether a V2NavItem is "active" given the current
- * route name.
- *
- * Active rules (simplest correct definition):
- * 1. Exact match: currentRouteName === item.to.name
- * 2. Prefix match for nested routes: currentRouteName starts with
- *    item.to.name + '-'  (e.g. item "organisation" is active on
- *    "organisation-settings"). The dash boundary prevents "org" from
- *    spuriously matching "organisation-settings".
- *
- * Only `to` values that are a plain object with a string `name` property are
- * compared — string/array `to` values always return false (router-push
- * style not used in v1 nav).
- */
-export function isNavItemActive(
-  item: V2NavItem,
-  currentRouteName: string | symbol | null | undefined,
-): boolean {
-  if (typeof currentRouteName !== 'string')
-    return false
-
-  const to = item.to
-
-  if (typeof to !== 'object' || to === null || Array.isArray(to))
-    return false
-
-  const itemName = (to as { name?: unknown }).name
-
-  if (typeof itemName !== 'string')
-    return false
-
-  return currentRouteName === itemName
-    || currentRouteName.startsWith(`${itemName}-`)
-}