feat(events): the minimal admin surface (Phase 3)

Three screens, an Events nav group and the six live run controls Phase 1 left
absent on purpose because nothing was in flight. An admin can now author,
publish, start and watch an event that announces things and cues a human; a
moderator can stop one that is going wrong.

Six controls, not eight. `advance` is absent because a phase today advances when
its steps go terminal — the per-step skip already does that — and Phase 5 is what
gives a phase an advance condition. Cancel takes `{ reason }`, not `{ cleanup }`,
until Phase 8's ledger exists. Every control is a compare-and-set on the status it
may act from, so a console rendered thirty seconds ago cannot act on a run that
has moved.

Fixes a defect in the Phase 2 runner: `advanceRun` drained up to
EVENT_STEPS_PER_TICK steps while only checking the run's status at the top of the
tick, so a pause pressed mid-batch did nothing for up to 24 more steps.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T6t8mrAWhZU5vnyYgZTMtL

server/routes.manifest.json

@@ -229,10 +229,34 @@
       "method": "GET",
       "path": "/api/v1/admin/events/runs/:runId"
     },
+    {
+      "method": "POST",
+      "path": "/api/v1/admin/events/runs/:runId/cancel"
+    },
     {
       "method": "GET",
       "path": "/api/v1/admin/events/runs/:runId/log"
     },
+    {
+      "method": "POST",
+      "path": "/api/v1/admin/events/runs/:runId/pause"
+    },
+    {
+      "method": "POST",
+      "path": "/api/v1/admin/events/runs/:runId/resume"
+    },
+    {
+      "method": "POST",
+      "path": "/api/v1/admin/events/runs/:runId/steps/:stepId/confirm"
+    },
+    {
+      "method": "POST",
+      "path": "/api/v1/admin/events/runs/:runId/steps/:stepId/retry"
+    },
+    {
+      "method": "POST",
+      "path": "/api/v1/admin/events/runs/:runId/steps/:stepId/skip"
+    },
     {
       "method": "GET",
       "path": "/api/v1/admin/events/series"