perf: skip Discovered messages during test execution

[thomhurst]

Summary

• Remove Discovered message loop from HandleRunRequestAsync during test execution
• Only send Discovered messages during discovery requests (for test explorers)
• Change DynamicTestQueue.EnqueueAsync to synchronous Enqueue method
• Dynamic tests created at runtime don't need discovery notifications since they're created during execution

Rationale

Discovered messages are used by test explorers to populate their UI during test discovery. When actually running tests, these messages are unnecessary overhead since:

1. The tests have already been discovered
2. The test session is in execution mode, not discovery mode
3. Dynamic tests (created via CreateTestVariant or AddDynamicTest) are created during execution, not discovery

Test plan

• Build succeeds with no errors
• Ran 10,218+ tests successfully
• Verified discovery requests still send Discovered messages

🤖 Generated with Claude Code

[thomhurst]

Summary

Removes unnecessary Discovered message overhead during test execution by skipping these notifications when running tests (they remain for discovery requests).

Critical Issues

None found ✅

Suggestions

None - the change is clean and well-reasoned:

• Discovery requests still send Discovered messages (TestRequestHandler.cs:48)
• Run requests skip them to avoid redundant overhead
• The async→sync change is safe (Channel.TryWrite is non-blocking for unbounded channels)
• Internal API only (no public API changes, no snapshot updates needed)

Verdict

✅ APPROVE - No critical issues

This is a solid performance optimization that removes unnecessary work during test execution while preserving correct behavior for test discovery.