feat(events): publish runId on a public calendar run entry (Rust D125)

A run entry on GET /public/events now names its run, the same id the
event page already publishes on each occurrence and `?run=` takes. A
Rust map marker carries core's run id and nothing else about its event,
so without this the app could only find the event by fetching every
event page.

A projected entry has no runId: nothing is committed to it. Rehearsals
and unlisted events stay absent from the calendar, so their markers
stay unlinked. The web calendar ignores the field.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

server/swagger/swagger.js

@@ -1247,6 +1247,12 @@ const doc = {
           'One calendar entry. `kind` says which of two things it is: a `run` is a materialised occurrence, a `projected` entry is arithmetic past the materialisation horizon — a forecast with nothing committed to it, which a client should draw as such.',
         properties: {
           kind: { type: 'string', enum: ['run', 'projected'], example: 'run' },
+          runId: {
+            type: 'integer',
+            example: 3692,
+            description:
+              'Runs only: the run this entry is, the same id `PublicEventOccurrence.runId` carries and `/events/{slug}?run=` takes. A projected entry has none, because nothing is committed to it.',
+          },
           title: { type: 'string', example: 'The Yew Invasion' },
           slug: { type: 'string', example: 'the-yew-invasion' },
           seriesName: { type: 'string', nullable: true, example: 'The Yew Campaign' },