feat(tasks): add task identification system

[kariy]

Summary

Implements unique task IDs for all tasks spawned via TaskManager to improve debugging and visibility during development.

Changes

• TaskId Type: Added a new TaskId type that uniquely identifies each spawned task

  • Implements Display, Debug, Clone, Copy, PartialEq, Eq, and Hash
  • IDs are generated sequentially using an atomic counter for thread-safety

• Shutdown Initiator Tracking: Tasks that trigger graceful shutdown are now tracked

  • Added shutdown_initiator field to store the ID of the task that initiated shutdown
  • Public method TaskManager::shutdown_initiator() returns the initiator task ID

• Enhanced Logging: All task completion and panic messages now include task IDs

  • Tasks with graceful shutdown log at info level with ID and name
  • Regular task completion logs at debug level with ID and name
  • Format: id = <task_id>, task = <optional_name>

• TaskBuilder Integration: Each TaskBuilder gets a unique ID when created

  • Added TaskBuilder::id() method to retrieve the task's ID before spawning
  • ID is automatically assigned when calling build_task()

Benefits

• Better Debugging: Identify exactly which task caused graceful shutdown
• Improved Tracing: All log messages include task IDs for easier task execution tracking
• Backward Compatible: Existing code continues to work without changes
• Thread-Safe: Uses atomic operations for ID generation

Usage Example

let manager = TaskManager::current();
let spawner = manager.task_spawner();

let task = spawner.build_task()
    .name("Block production")
    .graceful_shutdown()
    .spawn(some_future);

// Later, after shutdown:
if let Some(task_id) = manager.shutdown_initiator() {
    println!("Shutdown was initiated by task: {}", task_id);
}

Testing

• Updated existing tests to verify shutdown initiator tracking
• All tests pass successfully
• Code is properly formatted according to project standards

Closes DOJ-1071

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 77.33333% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.58%. Comparing base (9bde0ae) to head (f76ca1d).
⚠️ Report is 122 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/tasks/src/manager.rs	69.04%	13 Missing ⚠️
crates/tasks/src/spawner.rs	87.87%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #294      +/-   ##
==========================================
+ Coverage   73.32%   75.58%   +2.26%     
==========================================
  Files         209      230      +21     
  Lines       23132    27276    +4144     
==========================================
+ Hits        16961    20617    +3656     
- Misses       6171     6659     +488     

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