Phase 6: fix the live Home Assistant write (Local Calendar, no event id)

The first live run against the new calendar.school entity failed loudly twice,
and both causes are fixed here.

- The Local Calendar rejects `return_response` on calendar.create_event. The
  client retries the call without it and ignores the changed-states array that
  Home Assistant returns instead.
- Home Assistant then reports no event id. The item keeps the description
  marker ([compass-nhs:<id>]) as its reference, so it leaves the candidate set
  and is never written twice. The live retry proved it: both events already in
  the calendar were adopted by their markers, with no duplicate.
- calendar.get_events reports `start` / `end` (a date-time or a bare date), not
  `start_date_time`; the reader now accepts all three shapes.

A model must no longer classify events. The calendar write depends on the
school-event rule, and the LLM labelled every event "normal"; events now keep
the deterministic rule under both classifiers.

Also fix the Phase 5 screenshot script: the calendar banner shares the `.scan`
class, so select each banner by its labelled section.

Docs record the accepted decision: Sam chose a Home Assistant Local Calendar,
so the target is calendar.school.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

docs/phase-6-calendar-notes.md

@@ -1,8 +1,14 @@
 # Phase 6 — the calendar write (Sam's Home Assistant calendar)
 
-Status: **code complete and tested; the calendar target needs Sam's decision**
-(AUD-110). The service now writes important school events through the Home
-Assistant REST API. Nothing is written until a calendar entity is chosen.
+Status: **done** (AUD-110). Sam chose a **Home Assistant Local Calendar**, and
+the service writes important school events to it through the Home Assistant REST
+API.
+
+| | |
+|---|---|
+| Target entity | `calendar.school` (Local Calendar "School", added 2026-10-15) |
+| Configuration | `environment.d/school-service.env` (gitignored): `SCHOOL_HA_URL`, `SCHOOL_HA_TOKEN`, `SCHOOL_HA_CALENDAR_ENTITY`, `SCHOOL_HA_TIMEOUT` |
+| First live events | *Senior Sub-School Community Service for Uniform Infringement* and *End of Year Senior Music Concert — HALL* (2026-10-15) |
 
 ## What it does
 
@@ -82,32 +88,37 @@ scripts/calendar-push.sh push --dry-run --json
 The item screen has an **Add to calendar** button for an important future event,
 and shows `in the calendar` with the Home Assistant event id once it is written.
 
-## The open decision: which calendar entity?
+## Decision (accepted 2026-10-15)
 
-The Home Assistant instance (`192.168.20.30`, HA 2026.9.4) has three calendar
-entities, and only two are writable:
+The Home Assistant instance (`192.168.20.30`, HA 2026.9.4) had three calendar
+entities, and all the writable ones were Google-backed
+(`calendar.samuelrolfe_googlemail_com`, `calendar.birthdays`); the brief says
+**Sam's Home Assistant calendar (not Google)**, and no non-Google calendar
+existed. Sam chose to **add a Local Calendar**, so:
 
-| Entity | Writable | Backing |
-|---|---|---|
-| `calendar.samuelrolfe_googlemail_com` | yes | Google, synced into Home Assistant |
-| `calendar.birthdays` | yes | Google |
-| `calendar.holidays_in_australia` | no | Google |
+- The Local Calendar integration was added through the Home Assistant config
+  flow, creating the entity **`calendar.school`** (title "School"). It is
+  Home-Assistant-local, never touches Google, and the change is purely additive.
+- `SCHOOL_HA_CALENDAR_ENTITY=calendar.school`.
 
-The brief says **Sam's Home Assistant calendar (not Google)**. Today Home
-Assistant has **no non-Google writable calendar**: the `local_calendar`
-integration is not installed, and no CalDAV/remote calendar is configured.
+The calendar is a family calendar, so an event carries the child's name only
+when it belongs to one child.
 
-So the target must be chosen before the event is written:
+## Home Assistant quirks found on the first live run
 
-1. **Add a Local Calendar to Home Assistant** (recommended). One Home Assistant
-   config-flow entry creates `calendar.school`. It is Home-Assistant-local, never
-   touches Google, and is entirely additive. The service then uses
-   `SCHOOL_HA_CALENDAR_ENTITY=calendar.school`.
-2. **Use `calendar.samuelrolfe_googlemail_com`.** No Home Assistant change, but
-   every school event also appears in Sam's personal Google Calendar.
+Both are handled, and both were caught by the fail-loudly design rather than
+silently writing nothing:
 
-The question is posted on AUD-110. The code needs only the configuration line
-changed once the answer is in.
+- **The Local Calendar rejects `return_response`.** `calendar.create_event` is
+  called with the service response to learn the event id; the Local Calendar
+  answers `Service does not support responses`. The client retries the call
+  without it. Home Assistant then replies with the changed states, a JSON array,
+  which the client ignores.
+- **The Local Calendar reports no event id.** With no id to store, the item keeps
+  the description marker (`[compass-nhs:<item id>]`) as its reference, so the
+  item leaves the candidate set and is never written twice. The live retry
+  proved it: after a failed first attempt the two events already in the calendar
+  were adopted by their markers, and nothing was duplicated.
 
 ## Where the code lives
 
@@ -141,8 +152,12 @@ make test    # go test ./...
 ```
 
 The tests cover the Home Assistant client against a fake Home Assistant (create,
-read-back, error mapping), the sync run (write once, adopt by marker, dry run,
-loud failure, refuse-to-write-blind), the store (candidates, the push log) and
-the web surface (the action, the CSRF guard, the failure banner).
+read-back, error mapping, the no-response fallback, the `start`/`end` shapes),
+the sync run (write once, adopt by marker, dry run, loud failure,
+refuse-to-write-blind, no-event-id idempotency), the store (candidates, the push
+log), the parser (a model cannot label an event) and the web surface (the
+action, the CSRF guard, the failure banner).
 
-Not tested here: the live Home Assistant write. That needs the entity decision.
+Live proof on `.13` (2026-10-15): two Compass school events were written to
+`calendar.school`, read back through the Home Assistant API, and the dashboard
+and item screen show the calendar state.