Fix Maven Central publish signing in release workflow

[Copilot]

The Publish to Maven Central GitHub Actions job was failing during artifact signing because GPG was invoked in interactive pinentry mode. This change aligns the Maven/GPG configuration with non-interactive CI execution.

• Root cause

  • The release job imported the private key successfully, but maven-gpg-plugin still called gpg without loopback pinentry.
  • In GitHub Actions this caused gpg: signing failed: No pinentry during deploy.

• Build configuration

  • Configure maven-gpg-plugin to pass loopback pinentry arguments to GPG:
    • --pinentry-mode
    • loopback

• Release workflow

  • Pass the signing passphrase via MAVEN_GPG_PASSPHRASE in the publish step instead of GPG_PASSPHRASE.
  • This matches the Maven GPG plugin’s batch-mode convention for non-interactive signing.

• Result

  • Keeps Maven Central publishing behavior unchanged outside CI.
  • Removes the interactive pinentry requirement from the release path.

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-gpg-plugin</artifactId>
  <version>3.2.7</version>
  <configuration>
    <gpgArguments>
      <arg>--pinentry-mode</arg>
      <arg>loopback</arg>
    </gpgArguments>
  </configuration>
</plugin>