chore: enable pr-agent push trigger (#243)

Adds `handle_push_trigger = true` to the existing `[github_app]` table
in `.pr_agent.toml` so the PR agent (qodo) re-runs its review on pushes,
not only when a PR is opened.

Merged into the existing table rather than adding a second
`[github_app]` header (duplicate TOML table headers are invalid).

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Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: CoderCoco

.pr_agent.toml

@@ -1,4 +1,5 @@
 [github_app]
+handle_push_trigger = true
 pr_commands = [
     "/agentic_describe",
     "/agentic_review"