Add organizer cancel-event flow to EventList

Organizers can now cancel events directly from the event list via the
existing PATCH /events/{eventToken} API. The confirmation dialog shows
role-differentiated messaging: "Cancel event?" with a severity warning
for organizers vs. "Remove event?" for attendees. Responses 204, 409,
and 404 all result in successful removal from the local list.

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

specs/018-cancel-event-list/tasks.md

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+# Tasks: Cancel Event from Event List
+
+**Input**: Design documents from `/specs/018-cancel-event-list/`
+**Prerequisites**: plan.md, spec.md, research.md, data-model.md
+
+**Tests**: Mandatory per constitution (TDD — Red → Green → Refactor).
+
+**Organization**: Tasks are grouped by user story. No setup or foundational phases needed — all infrastructure exists.
+
+## Format: `[ID] [P?] [Story] Description`
+
+- **[P]**: Can run in parallel (different files, no dependencies)
+- **[Story]**: Which user story this task belongs to (e.g., US1, US2)
+- Include exact file paths in descriptions
+
+---
+
+## Phase 1: User Story 1 — Organizer Cancels Event from List (Priority: P1) 🎯 MVP
+
+**Goal**: Organizers can cancel an event directly from the event list via confirmation dialog and PATCH API call.
+
+**Independent Test**: Create an event, navigate to event list, tap delete on organizer event, confirm in dialog, verify API call is made and event is removed from list.
+
+### Tests for User Story 1 ⚠️
+
+> **NOTE: Write these tests FIRST, ensure they FAIL before implementation**
+
+- [X] T001 [P] [US1] E2E test: organizer taps delete, confirms, event is removed after successful API call in `frontend/e2e/cancel-event-list.spec.ts`
+- [X] T002 [P] [US1] E2E test: organizer confirms cancellation, API fails, event stays in list and error message shown in `frontend/e2e/cancel-event-list.spec.ts`
+- [X] T003 [P] [US1] E2E test: organizer confirms cancellation, API returns 409 Conflict, event is silently removed from list in `frontend/e2e/cancel-event-list.spec.ts`
+- [X] T004 [P] [US1] E2E test: organizer opens cancel dialog then dismisses (cancel button, Escape, overlay click), event remains unchanged in `frontend/e2e/cancel-event-list.spec.ts`
+- [X] T005 [P] [US1] Unit test: `confirmDelete` calls PATCH cancel-event API when role is organizer in `frontend/src/components/__tests__/EventList.spec.ts`
+- [X] T006 [P] [US1] Unit test: `confirmDelete` treats 409 response as success (removes event from list) in `frontend/src/components/__tests__/EventList.spec.ts`
+
+### Implementation for User Story 1
+
+- [X] T007 [US1] Extend `confirmDelete` in `frontend/src/components/EventList.vue` to detect organizer role and call `api.PATCH('/events/{eventToken}')` with `{ cancelled: true }` and `organizerToken` query param
+- [X] T008 [US1] Handle 409 Conflict as success (silently remove event from local list) in `frontend/src/components/EventList.vue`
+- [X] T009 [US1] Handle API errors (keep dialog open, show error message) for organizer cancel in `frontend/src/components/EventList.vue`
+- [X] T010 [US1] Add organizer-specific dialog title ("Cancel event?") and message ("This will permanently cancel the event for all attendees.") in `frontend/src/components/EventList.vue`
+
+**Checkpoint**: Organizer can cancel events from the list. E2E and unit tests pass green.
+
+---
+
+## Phase 2: User Story 2 — Distinct Dialog for Organizer vs. Attendee (Priority: P2)
+
+**Goal**: Confirmation dialog clearly differentiates between organizer cancellation (severe, affects everyone) and attendee RSVP cancellation (personal).
+
+**Independent Test**: Compare dialog text when deleting as organizer vs. as attendee for the same event — organizer dialog must have stronger warning.
+
+### Tests for User Story 2 ⚠️
+
+> **NOTE: Write these tests FIRST, ensure they FAIL before implementation**
+
+- [X] T011 [P] [US2] E2E test: organizer dialog shows event-cancellation warning (title + message distinct from attendee) in `frontend/e2e/cancel-event-list.spec.ts`
+- [X] T012 [P] [US2] E2E test: attendee dialog preserves existing RSVP-cancellation message (no regression) in `frontend/e2e/cancel-event-list.spec.ts`
+- [X] T013 [P] [US2] Unit test: `deleteDialogMessage` and `deleteDialogTitle` return organizer-specific text when `getRole()` is organizer in `frontend/src/components/__tests__/EventList.spec.ts`
+- [X] T014 [P] [US2] Unit test: `deleteDialogMessage` returns existing attendee text unchanged when `getRole()` is attendee in `frontend/src/components/__tests__/EventList.spec.ts`
+
+### Implementation for User Story 2
+
+- [X] T015 [US2] Refactor `deleteDialogMessage` computed in `frontend/src/components/EventList.vue` to return role-differentiated text: organizer warning vs. existing attendee message
+- [X] T016 [US2] Add `deleteDialogTitle` computed in `frontend/src/components/EventList.vue` returning "Cancel event?" for organizer, "Remove event?" for attendee
+- [X] T017 [US2] Bind `deleteDialogTitle` to ConfirmDialog `:title` prop in `frontend/src/components/EventList.vue`
+
+**Checkpoint**: Dialog messages are clearly differentiated by role. All E2E and unit tests pass green.
+
+---
+
+## Phase 3: Polish & Cross-Cutting Concerns
+
+**Purpose**: Final validation and regression check
+
+- [X] T018 Run full frontend unit test suite (`npm run test:unit`) — verify no regressions
+- [X] T019 Run full E2E test suite (`npx playwright test`) — verify no regressions
+- [X] T020 Verify existing attendee and watcher delete flows unchanged (FR-007) via E2E tests
+
+---
+
+## Dependencies & Execution Order
+
+### Phase Dependencies
+
+- **Phase 1 (US1)**: No dependencies — can start immediately (all infrastructure exists)
+- **Phase 2 (US2)**: Depends on Phase 1 completion (US2 refines the dialog created in US1)
+- **Phase 3 (Polish)**: Depends on Phase 1 + Phase 2 completion
+
+### User Story Dependencies
+
+- **US1 (P1)**: Independent — core cancel flow + initial dialog message
+- **US2 (P2)**: Depends on US1 — refines dialog messaging created in US1
+
+### Within Each User Story
+
+- Tests MUST be written and FAIL before implementation (TDD)
+- Implementation tasks are sequential within each story (T007 → T008 → T009 → T010)
+- All test tasks within a story can run in parallel
+
+### Parallel Opportunities
+
+- T001–T006 (US1 tests): All parallelizable — different test scenarios, same files but independent
+- T011–T014 (US2 tests): All parallelizable
+- US1 and US2 are sequential (US2 depends on US1)
+
+---
+
+## Parallel Example: User Story 1
+
+```bash
+# Launch all US1 tests in parallel (TDD — write first, expect red):
+Task: "E2E test: organizer cancels event successfully" (T001)
+Task: "E2E test: organizer cancel fails, error shown" (T002)
+Task: "E2E test: 409 Conflict handled as success" (T003)
+Task: "E2E test: dismiss dialog, event unchanged" (T004)
+Task: "Unit test: confirmDelete calls PATCH for organizer" (T005)
+Task: "Unit test: 409 treated as success" (T006)
+
+# Then implement sequentially:
+Task: "Extend confirmDelete for organizer role" (T007)
+Task: "Handle 409 Conflict" (T008)
+Task: "Handle API errors" (T009)
+Task: "Add organizer dialog title + message" (T010)
+```
+
+---
+
+## Implementation Strategy
+
+### MVP First (User Story 1 Only)
+
+1. Write US1 tests (T001–T006) — all should fail (red)
+2. Implement US1 (T007–T010) — tests turn green
+3. **STOP and VALIDATE**: Organizer can cancel events from list
+4. Deploy/demo if ready
+
+### Full Delivery
+
+1. Complete US1 → MVP functional
+2. Complete US2 → Dialog messaging polished
+3. Complete Polish → Full regression validation
+
+---
+
+## Notes
+
+- No backend changes required — existing PATCH `/events/{eventToken}` endpoint used
+- No new components — ConfirmDialog reused as-is
+- No new dependencies
+- Primary change: ~50 lines in `EventList.vue` + tests