[None][infra] fix cbts json decode

[crazydemo]

This PR is for fixing cbts failure with:
[2026-06-02T23:46:12.311Z] CBTS failed, falling back to full run: org.jenkinsci.plugins.scriptsecurity.sandbox.RejectedAccessException: Scripts not permitted to use method java.lang.String getBytes java.nio.charset.Charset
https://prod.blsm.nvidia.com/sw-tensorrt-top-1/blue/organizations/jenkins/LLM%2Fmain%2FL0_MergeRequest_PR/detail/L0_MergeRequest_PR/41078/pipeline/22/

Summary by CodeRabbit

Release Notes

• Refactor

  • Updated CBTS payload encoding and decoding methods to use default character encoding instead of explicit UTF-8 specification.

• Chores

  • Removed unused import statements from build scripts.

Description

Test Coverage

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📝 Walkthrough

Walkthrough

The PR simplifies CBTS piggyback payload handling in two Groovy test infrastructure files by removing explicit UTF-8 charset specifications. The encoding operation in L0_MergeRequest.groovy and the decoding operation in L0_Test.groovy now rely on implicit platform default charset, and the StandardCharsets import is removed.

Changes

CBTS Payload Character Encoding

Layer / File(s)	Summary
CBTS payload encoding change jenkins/L0_MergeRequest.groovy	In getCbtsResult, CBTS Layer 3 piggyback base64 encoding switched from explicit UTF-8 (StandardCharsets.UTF_8) to implicit charset via inputJson.bytes, affecting both the generated base64 content and the size calculation for downstream stages.
CBTS payload decoding and import cleanup jenkins/L0_Test.groovy	In renderTestDB, CBTS piggyback payload decoding now constructs the String from decoded bytes without an explicit charset parameter; the now-unused StandardCharsets import was removed.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The PR description is incomplete and lacks required details. Only an error message is provided with no explanation of the fix or test coverage.	Provide a clear explanation of the issue, the root cause, the solution implemented, and list relevant test cases that validate the fix.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: fixing CBTS JSON decoding in infrastructure scripts by switching from explicit UTF-8 charset to default bytes handling.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@jenkins/L0_MergeRequest.groovy`:
- Line 782: The base64 encoding of inputJson uses platform default charset which
can corrupt non-ASCII content; change the encoding to use UTF-8 by getting bytes
with StandardCharsets.UTF_8 when building inputJsonB64 (replace inputJson.bytes
usage), and mirror this on decode in L0_Test.groovy by constructing
cbtsInputJson with new String(cbts.cbts_input_json_b64.decodeBase64(),
StandardCharsets.UTF_8); also add/import java.nio.charset.StandardCharsets in
both files so the charset symbol is available.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

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ℹ️ Review info

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Run ID: 4ff1f358-3cf3-47c5-b77e-52335c607c37

📥 Commits

Reviewing files that changed from the base of the PR and between d64b217 and 8dabe49.

📒 Files selected for processing (2)

• jenkins/L0_MergeRequest.groovy
• jenkins/L0_Test.groovy

[tensorrt-cicd]

PR_Github #51943 [ run ] triggered by Bot. Commit: 8dabe49 Link to invocation

[tensorrt-cicd]

PR_Github #51943 [ run ] completed with state FAILURE. Commit: 8dabe49
/LLM/main/L0_MergeRequest_PR pipeline #41294 completed with status: 'FAILURE'

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PR_Github #52012 [ run ] completed with state SUCCESS. Commit: c10a386
/LLM/main/L0_MergeRequest_PR pipeline #41354 (Partly Tested) completed with status: 'SUCCESS'

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PR_Github #52034 [ reuse-pipeline ] completed with state SUCCESS. Commit: c10a386
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