Fixed Java SDK cordinator-mode not retrying failed tasks

[onlyarnav]

This PR fixes an issue where the Java SDK reports every task failure as a terminal TaskState(FAILED) frame in coordinator mode, preventing retries from taking effect.
The Java runtime SDK's Task.kt has been updated to check for shouldRetry inside the task context, properly returning a RetryTask when true.
Tests have been included and verified against Gradle.

Issue Fixed: #67798

Was generative AI tooling used to co-author this PR?

• Yes — Claude Code (Opus 4.8)

[boring-cyborg]

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[onlyarnav]

@jason810496 can you please review the PR and approve or suggest changes