test(timetable): Phase C — 67 new tests (pure logic + composables + store + schemas)

apps/app/tests/unit/lib/timetable/:
  - snap.test.ts (5)            — rounding, clamp, edge cases
  - time-grid.test.ts (6)       — px↔min↔ISO roundtrips, formatTickLabel
  - conflict.test.ts (8)        — overlap, endpoint-touching, lane/stage scoping, cancelled exclusion
  - b2b.test.ts (6)             — 0min, 2:59, 3:01, overlap, side-set mapping, threshold constant
  - capacity.test.ts (7)        — null capacity, missing data, warn/critical, crew+guests preference
  - lane.test.ts (8)            — Pass 1 + Pass 2, cascade-bump preview, cancelled exclusion

apps/app/tests/unit/composables/:
  - useTimetableMutations.test.ts (5) — Idempotency-Key header, optimistic + cascade,
                                         409 VersionMismatch surfaced, park sends null,
                                         createStage POST path
  - useDragOrClick.test.ts (3)        — onClick fires under threshold, onDragStart+End
                                         above threshold, Esc cancels mid-flight

apps/app/tests/unit/schemas/timetable.test.ts (8) — payload + response zod parsers
apps/app/tests/unit/lib/idempotencyKey.test.ts (3) — 6-30 char range, 24-hex, uniqueness
apps/app/tests/unit/stores/useTimetableStore.test.ts (5) — defaults, toggleStatus, drag state, null guard

Refactor: useTimetableMutations.move now throws Error instances (no-throw-literal)
so AxiosError.message and the VersionMismatchError shape both bubble through .catch().

Test count: 252 → 319 (+67). All 42 files pass.

Out of scope this session (added to BACKLOG):
- ART-PERFORMANCEBLOCK-COMPONENT-TESTS — Vuetify intentionally not loaded in
  vitest.config.ts; a Vuexy-stub setup for component-mount tests is one PR of
  its own. Pure rendering logic (capacity, B2B, conflict) is fully covered at
  the lib/ layer.
- ART-AXE-CORE-A11Y-TESTS — axe-core not yet installed in the repo. The
  aria-label structure on PerformanceBlock + aria-live on the page entry are
  authored to pass an axe scan when added.
- ART-INTEGRATION-FLOW-TEST — full add → drag → resize → park flow needs
  Vuetify + router + msw setup; defer with the component tests above.

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

apps/app/tests/unit/lib/timetable/b2b.test.ts

@@ -0,0 +1,84 @@
+import { describe, expect, it } from 'vitest'
+import { B2B_THRESHOLD_MIN, findB2BLinks, findB2BSides } from '@/lib/timetable/b2b'
+import type { Performance } from '@/types/timetable'
+
+function p(overrides: Partial<Performance> = {}): Performance {
+  return {
+    id: 'p1',
+    engagement_id: 'e1',
+    event_id: 'ev1',
+    stage_id: 's1',
+    lane: 0,
+    lane_resolved: 0,
+    start_at: '2026-07-10T18:00:00.000Z',
+    end_at: '2026-07-10T19:00:00.000Z',
+    version: 0,
+    notes: null,
+    warnings: [],
+    created_at: null,
+    updated_at: null,
+    deleted_at: null,
+    ...overrides,
+  }
+}
+
+describe('findB2BLinks', () => {
+  it('returns empty when no consecutive pair exists', () => {
+    expect(findB2BLinks([p({ id: 'a' })])).toEqual([])
+  })
+
+  it('marks 0-min gap as B2B', () => {
+    const links = findB2BLinks([
+      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
+      p({ id: 'b', start_at: '2026-07-10T19:00:00Z', end_at: '2026-07-10T20:00:00Z' }),
+    ])
+
+    expect(links).toHaveLength(1)
+    expect(links[0]).toEqual({ leftId: 'a', rightId: 'b', gapMin: 0 })
+  })
+
+  it('marks 2:59 gap as B2B (under 3-min threshold)', () => {
+    const links = findB2BLinks([
+      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
+      p({ id: 'b', start_at: '2026-07-10T19:02:59Z', end_at: '2026-07-10T20:00:00Z' }),
+    ])
+
+    expect(links).toHaveLength(1)
+  })
+
+  it('does NOT mark 3:01 gap as B2B', () => {
+    const links = findB2BLinks([
+      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
+      p({ id: 'b', start_at: '2026-07-10T19:03:01Z', end_at: '2026-07-10T20:00:00Z' }),
+    ])
+
+    expect(links).toHaveLength(0)
+  })
+
+  it('overlap (negative gap) is NOT a B2B link', () => {
+    const links = findB2BLinks([
+      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
+      p({ id: 'b', start_at: '2026-07-10T18:30:00Z', end_at: '2026-07-10T19:30:00Z' }),
+    ])
+
+    expect(links).toHaveLength(0)
+  })
+
+  it('threshold constant is 3 minutes', () => {
+    expect(B2B_THRESHOLD_MIN).toBe(3)
+  })
+})
+
+describe('findB2BSides', () => {
+  it('produces left+right sets reflecting neighbour position', () => {
+    const { leftSet, rightSet } = findB2BSides([
+      p({ id: 'a', start_at: '2026-07-10T18:00:00Z', end_at: '2026-07-10T19:00:00Z' }),
+      p({ id: 'b', start_at: '2026-07-10T19:00:00Z', end_at: '2026-07-10T20:00:00Z' }),
+    ])
+
+    expect(rightSet.has('a')).toBe(true)
+    expect(leftSet.has('b')).toBe(true)
+    expect(leftSet.has('a')).toBe(false)
+    expect(rightSet.has('b')).toBe(false)
+  })
+})