Replace parallel logs with live-updating table

[viamus]

Summary

• Replaced chaotic interleaved console output during parallel execution with a clean live-updating table using Spectre.Console Live
• New ParallelLiveTable class manages per-item state with thread-safe updates
• Both ParallelForeachStep and ParallelStep now use the live table
• Elapsed timers refresh every second for running items

Before

Chaotic interleaved thinking/tool_use lines from multiple concurrent items — impossible to follow:

After

Clean in-place table with real-time status per item:

  Status     │ Item                                 │ Activity
 ────────────┼──────────────────────────────────────┼──────────────────────────
  ✔  1m 10s  │ Name1             │ 62,169 tokens  $0.0751
  ✘  1m 12s  │ Name2                           │ 61,692 tokens  $0.0737
  ○    45s   │Name3                       │ Bash: dotnet script
  ○    38s   │ Name14                               │ Reading file...
  ◌          │ Name1     123                   │ waiting
  ◌          │ Name1          1234                    │ waiting

Status icons: ◌ waiting · ○ running · ✔ success · ✘ failed

Files Changed

File	Change
UI/ParallelLiveTable.cs	New — thread-safe live table with per-item state, elapsed timers, metrics
UI/PipelineRenderer.cs	Replaced parallel render methods with RunParallelWithLiveTable() + RenderParallelSummary()
Steps/ParallelForeachStep.cs	Refactored to use live table callbacks
Steps/ParallelStep.cs	Refactored to use live table callbacks

Test plan

• All 111 tests pass (dotnet test)
• Visual test with a real parallel_foreach pipeline
• Verify sequential foreach and normal steps are unaffected
• Verify fail_fast cancellation still works correctly

🤖 Generated with Claude Code