feat(web): add automatic actions for open pull requests

A new pr_open alert carries the head commit SHA of each open, non-draft, same-repository pull request. An action with auto enabled sends its webhook once for each pull request and head commit. An authors list limits which pull requests trigger it. The alert never changes repository health.

config.example.yaml

@@ -25,6 +25,13 @@ thresholds: # negative disables a check
 #       timeout: 10s
 #     status_url: https://example.internal/hooks/rerun/status # optional
 #     confirm: "Run this action for the selected alert?" # optional; omit for no dialog
+#   - id: review
+#     kinds: [pr_open] # required with auto; one alert per open, non-draft, non-fork PR
+#     auto: true # fire without a click, once per repo, PR and head commit
+#     authors: [lukaszraczylo] # optional; case-insensitive; omit for any author
+#     webhook:
+#       url: https://example.internal/hooks/review
+#       token_env: ACTION_TOKEN
 
 max_items: 100 # per repo, issues and PRs
 concurrency: 2