Run CI nightly and on manual dispatch

Pushes to main already trigger a full run, so code changes were
covered. What was not: the live tests depend on external state that
drifts with no commit at all — the LiteLLM budget filling up, a model
withdrawn from the proxy, a token revoked or expired. A nightly run
against the default branch surfaces that the morning it happens
instead of mid-task.

workflow_dispatch adds a manual trigger, which also removes the need
for the empty-commit trick used earlier to pick up new secrets.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -2,6 +2,15 @@ name: CI
 on:
   push:
   pull_request:
+  # Every push to main already runs this. The schedule catches what a commit
+  # cannot: the live tests depend on external state that drifts on its own —
+  # LiteLLM budget exhaustion, a model withdrawn from the proxy, a revoked
+  # Matrix or Gitea token. Nightly against the default branch surfaces that
+  # the morning it happens rather than mid-task.
+  schedule:
+    - cron: '17 6 * * *'
+  # Manual re-run, e.g. after rotating a credential or raising a budget cap.
+  workflow_dispatch:
 
 jobs:
   checks: