docs(release): add 0.15.1 notes (Trusted Publishing pipeline)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: lesnik512

planning/releases/0.15.1.md

@@ -0,0 +1,11 @@
+# httpware 0.15.1 — release pipeline on PyPI Trusted Publishing
+
+No library changes. The package is identical to 0.15.0; this release exercises the new publish path end-to-end.
+
+## CI
+
+- Releases now authenticate to PyPI via **Trusted Publishing (OIDC)** instead of a long-lived `PYPI_TOKEN` secret. `uv publish` auto-detects the GitHub Actions id-token; the release job runs under a `pypi` environment that scopes the trusted publisher (#89).
+
+## Downstream
+
+No action required. Nothing about the installed package changes.