chore: remove unnecessary nightly workflow

- Nightly builds were running on every push (wasteful)
- Not publishing artifacts (no value)
- Duplicating release workflow efforts
- Project does frequent releases, making nightlies redundant

For a project with regular releases (v0.10.0-as.1 through as.6),
nightly builds add complexity without clear benefit.

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: jackspirou