Docs: filed PRs must be opened in Frank's browser immediately

Trunk-based SDLC gains the delivery habit: xdg-open the PR URL the moment
it's filed (mirrors dank/serverAppConfigs step 6, riding their PR #6).
Changelog entry added.

AGENTS.md

@@ -34,6 +34,8 @@ with YAML frontmatter, spec at `omp-docs/references/okf-spec.md`).
 - Branch naming: `<type>/<issue#>-<slug>`, type ∈ feat|fix|docs|chore.
 - **Pull requests target `main` directly.** Merge with `--no-ff` so feature arcs
   stay visible in history. **Never merge a PR without an explicit OK from Frank.**
+- **The moment a PR is open, open it in Frank's browser** — `xdg-open <PR-URL>`
+  lands a tab in his Firefox; never make him hunt for it in Gitea.
 - Releases: tag `vX.Y.Z` straight on `main` after verifying; tags are the deploy
   markers every other machine pulls to. Hotfixes are ordinary branches off the
   tag you are fixing forward from.