feat: add normalizeForEngine function to process client payloads

[yeelali14]

✨ PR Description

Purpose: Add normalizeForEngine function to convert client payloads into gitstream-core's expected format before engine processing.

Main changes:

• Implemented normalizeForEngine function handling compressed, oversized-payload reference, and bare base64(gzip) formats
• Modified run function to output normalized client_payload via toStepOutputs and export normalizeForEngine for testing
• Updated action.yml to use normalized client_payload output instead of raw input, with comprehensive test coverage

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[orca-security-us]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	OSS Licenses	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

[linearb]

✨ PR Review

LGTM

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[MishaKav]

LGTM