Fix API tracker to use runtime Java version instead of hardcoded Java 24

[Copilot]

What changed

• Modified ApiTracker.java to dynamically detect Java version using Runtime.version().feature() instead of hardcoding --release 24
• Added comprehensive upstream API comparison report documenting breaking changes

Why this change is needed

The API tracker failed on Java 21 with "release version 24 not supported" errors, preventing upstream sync monitoring. The hardcoded version assumption broke the daily CI workflow and local development.

Upstream Changes Detected (7/11 classes affected):

• Json: fromUntyped() → toJson(), toUntyped() → fromJson()
• JsonArray: values() → elements(), added array()
• JsonBoolean: value() → bool()
• JsonNumber: Removed toNumber()/toBigDecimal(), added toLong()/toDouble(), changed of(BigDecimal) → of(long)
• JsonParseException: getErrorRow() → getErrorLine(), getErrorColumn() → getErrorPosition()
• JsonString: value() → string()
• JsonObject: Added object()

Full analysis in updates/api-check-2025-12-02.md

How were these changes tested

• Existing API tracker test suite (11/11 passing)
• Successful execution against live upstream: https://github.com/openjdk/jdk-sandbox/tree/json
• Code review and security scan completed

Checklist

• Code builds / passes tests
• New tests added if needed
• Update to use CODING_STYLE_LLM.md convensions
• Documentation updated if needed
• AGENTS.md updated if appropriate

Original prompt

please run the checker module to see if the upstream has got

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