Stream shell output to the TUI tail

[CalvinSturm]

Summary

Streams host shell stdout/stderr live into the existing TUI/log tail while preserving the final shell result envelope.

Long-running shell commands now show progress during execution instead of appearing inactive until completion.

What changed

• Added live ShellOutputChunk events for host shell stdout/stderr

• Threaded optional shell streaming through shell execution only

• Rendered live shell chunks in the existing TUI/log tail

• Displays stdout as out> and stderr as err>

• Preserved the final shell result envelope:

  • stdout
  • stderr
  • truncation flags
  • timed_out
  • timeout_ms
  • status

• Kept CLI projected JSON unchanged

• Kept JSONL/tail event output bounded

Memory and throttling behavior

• Live shell forwarding uses a bounded Tokio channel of 128 chunks
• Producers use best-effort try_send
• Noisy live output can drop progress chunks without affecting the final captured stdout/stderr
• Agent-side live output is capped at 64 KiB per command
• When the live cap is reached, a notice is emitted:
  [live output truncated; see final result]
• TUI log growth remains bounded by the existing max_log_lines

Why

PR #15 made shell execution bounded.
PR #16 preserved useful head/tail output after completion.
PR #17 added a default timeout policy.

This PR closes the remaining shell UX gap: the user can now see command progress while a long shell command is still running.

Validation

• cargo fmt --check
• cargo clippy --all-targets -- -D warnings
• focused live stream/TUI tests
• cargo test --lib target::
• cargo test --lib tools::
• cargo test --test tool_call_accuracy_ci
• cargo test --lib repro
• cargo test --test artifact_golden
• python scripts/ci_release_readiness.py
• cargo test

All validation passed locally.

Follow-ups

• Add deliberate CLI live shell display through a projected-event/display path
• Add Docker live streaming after Docker timeout semantics are addressed
• Robust process-tree cleanup
• Lightweight in-run todo/update_plan tool