chore(github-actions): fine tune workflow orchestrator defaults (#30794)

Issue number: resolves #

---------

<!-- Please do not submit updates to dependencies unless it fixes an
issue. -->

<!-- Please try to limit your pull request to one type (bugfix, feature,
etc). Submit multiple pull requests if needed. -->

## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->

- "nightly" was the default choice and was available for manual trigger
when running `release-orchestrator`

## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->

- Set "dev" as the default choice (changed from "nightly")
- Removed "nightly" from manual workflow_dispatch options (only "dev"
and "production" remain)
- Simplified the `run-nightly` condition to only run on schedule
(`github.event_name == 'schedule'`)


## Does this introduce a breaking change?

- [ ] Yes
- [-] No

<!--
  If this introduces a breaking change:
1. Describe the impact and migration path for existing applications
below.
  2. Update the BREAKING.md file with the breaking change.
3. Add "BREAKING CHANGE: [...]" to the commit description when merging.
See
https://github.com/ionic-team/ionic-framework/blob/main/docs/CONTRIBUTING.md#footer
for more information.
-->


## Other information

<!-- Any other information that is important to this PR such as
screenshots of how the component looks before and after the change. -->

- Manual triggers (workflow_dispatch): Only "dev" (default) and
"production" are available
- Scheduled triggers: The nightly build continues to run automatically
every Monday–Friday at 6:00 UTC via the schedule trigger
- Trusted Publishers compliance: Maintained — all releases still go
through the single orchestrator workflow, ensuring the OIDC token is
issued from the whitelisted workflow