ci: DH-21630: Add an option to specify custom remote

[vbabich]

Current tools/release.sh requires the git remote to be named origin. Added an option to allow custom remote; in my setup, I use upstream and origin instead of origin and fork.

Closes #787

[Copilot]

Pull request overview

This PR adds functionality to specify a custom git remote when running the release script, addressing issue DH-21630. This is useful when developers have their origin pointing to a fork and want to release to the upstream repository instead.

Changes:

• Added --remote / -r flag to the release script with validation
• Updated cog.toml to use the RELEASE_REMOTE environment variable with fallback to origin
• Updated documentation in README.md to explain the new flag usage

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
tools/release.sh	Added --remote argument parsing, validation of remote existence, and environment variable export
cog.toml	Updated git push commands to use ${RELEASE_REMOTE:-origin} variable
package-lock.json	Version bump for pivot plugin (appears unrelated to PR purpose)
README.md	Documented the new --remote flag with usage example

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

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