fix(sdk): use java duration for command request timeouts

[ninan-nn]

Summary

• Use java.time.Duration as the primary command timeout type for the Kotlin sandbox SDK.
• Keep deprecated kotlin.time.Duration overloads for RunCommandRequest, RunInSessionRequest, and the Commands.runInSession(...) convenience API so existing Kotlin builder-style callers can migrate gradually.
• Update command request serialization to convert Java durations with toMillis() while keeping the wire timeout value in milliseconds.
• Bump the Kotlin sandbox SDK version and default User-Agent from 1.0.11 to 1.0.12.
• Closes [Bug] Cannot call RunCommandRequest.Builder#timeout(Duration) from Java code due to Kotlin name mangling #849

Testing

• Unit tests: cd sdks/sandbox/kotlin && ./gradlew :sandbox:test
• Formatting: cd sdks/sandbox/kotlin && ./gradlew spotlessCheck
• Integration tests
• e2e / manual verification

Compatibility

• Java callers can now use java.time.Duration directly for command timeouts.
• Existing Kotlin callers that pass kotlin.time.Duration to the supported overloads continue to compile, but those overloads are deprecated in favor of java.time.Duration.
• Code that directly reads request.timeout now receives java.time.Duration? instead of kotlin.time.Duration? and may need a small migration.

Checklist

• Linked Issue or clearly described motivation
• Added/updated docs (if needed)
• Added/updated tests (if needed)
• Security impact considered
• Backward compatibility considered

[chatgpt-codex-connector]

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[Pangjiping]

LGTM

[chatgpt-codex-connector]

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Reviewed commit: e07b9fde00

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[Pangjiping]

LGTM