Add Jvm object monitor and remove rust_object_field from Object/Thread

[dlunch]

Summary

• Add object_wait, object_listen, object_notify methods to Jvm backed by a per-object Event monitor table
• Replace Arc<Event> stored via rust_object_field in Object.waitEvent and Thread.joinEvent with Jvm-level monitor
• Thread.join now uses object_listen + alive check pattern to avoid race condition (listen registered before condition check)
• Thread.isAlive now returns actual alive state instead of stub true
• Removes waitEvent: [B from Object, joinEvent: [B from Thread, adds alive: Z to Thread

This completes removal of all rust_object_field usage from java_runtime. Only java_lang_class.rs (jvm crate) remains, using byte array for class name due to circular dependency with String class.

[chatgpt-codex-connector]

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[codecov]

Codecov Report

❌ Patch coverage is 84.21053% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.60%. Comparing base (303f581) to head (b689ca9).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
java_runtime/src/classes/java/lang/thread.rs	64.28%	5 Missing ⚠️
java_runtime/src/classes/java/lang/object.rs	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #138      +/-   ##
==========================================
- Coverage   78.76%   78.60%   -0.17%     
==========================================
  Files         178      178              
  Lines        7286     7287       +1     
==========================================
- Hits         5739     5728      -11     
- Misses       1547     1559      +12     

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[Copilot]

Pull request overview

This PR moves object/thread wait/notify mechanics out of rust_object_field storage and into a JVM-managed per-object monitor table, and updates java.lang.Thread/java.lang.Object to use it.

Changes:

• Added Jvm::{object_listen, object_wait, object_notify} backed by a JVM-level monitor map.
• Replaced Object.waitEvent / Thread.joinEvent rust-object-field storage with JVM monitors and a new Thread.alive field.
• Updated Thread.join to register a listener before checking liveness, and implemented Thread.isAlive to reflect actual state.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
jvm/src/jvm.rs	Adds JVM-level monitor storage and APIs for object wait/notify.
jvm/Cargo.toml	Introduces the event-listener dependency for monitor implementation.
java_runtime/src/classes/java/lang/thread.rs	Reworks Thread join/isAlive to use JVM monitors and a new alive field.
java_runtime/src/classes/java/lang/object.rs	Reworks Object.wait/notify to use JVM monitors rather than per-object rust fields.
Cargo.lock	Locks the new dependency.

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