Improve PyPI release instructions in template_usage.md (#490)

* Initial plan

* Improve PyPI instructions in template_usage.md

Port improvements from scverse/cookiecutter-scverse-instance#207:
- Clarify that tags need to be released (not just pushed) to trigger the workflow
- Add note about pending publishers and first release
- Use reference-style links per maintainer preference

Closes #489

Agent-Logs-Url: https://github.com/scverse/cookiecutter-scverse/sessions/9c580dbc-9bdd-42a3-bf79-f2e539325f63

Co-authored-by: grst <7051479+grst@users.noreply.github.com>

* Manual fixes

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: grst <7051479+grst@users.noreply.github.com>
Co-authored-by: Gregor Sturm <gregor.sturm@boehringer-ingelheim.com>

Author: Copilot

{{cookiecutter.project_name}}/docs/template_usage.md

@@ -147,7 +147,8 @@ There you can see the execution history, logs, and (re-)trigger workflows manual
 
 ## Automating the PyPI release using GitHub actions
 
-Tags adhering to `"*.*.*"` that are pushed to the `main` branch will trigger the release Github workflow that automatically builds and uploads the Python package to [PyPI][].
+Releases created via the [Github releases UI][github-releases]
+will trigger the release Github workflow that automatically builds and uploads the Python package to [PyPI][].
 
 For this to work, you'll need to setup GitHub as a [trusted publisher][] on PyPI.
 To set this up, login to [PyPI][], and proceed depending on whether you already have your project on there or not:
@@ -159,6 +160,10 @@ The "Workflow name" needs to bet set to `release.yaml`.
 Set "Environment name" to “pypi” to match `environment: pypi` in `.github/workflows/release.yaml`.
 For more details, please refer to the official [PyPI guide for setting up trusted publishing][trusted publisher].
 
+If you added a new pending publisher to set up your project,
+the project will be published only once you release your package for the first time (see above).
+
+[github-releases]: https://docs.github.com/en/repositories/releasing-projects-on-github/about-releases
 [pypi-trusted-publishing-guide]: https://docs.pypi.org/trusted-publishers/adding-a-publisher/
 
 [PyPI]: https://pypi.org/