exec tool: support interactive CLI prompts

[carletex]

Current exec tool uses execFile with no stdin — can't handle interactive CLI prompts (e.g. npx create-eth@latest).

Options

1. Non-interactive flags (no code change)

Most CLIs have flags to skip prompts (--yes, --skip-install, etc). Agent just needs to know them.

2. Pipe stdin with spawn

Write all answers upfront to stdin. Simple but blind — breaks if prompt order changes.

3. Read stdout, respond to stdin

Stream output, pattern-match prompts, write appropriate input. Reactive but brittle.

4. PTY via node-pty

Full terminal emulation. Handles TUIs, arrow keys, ANSI. Heavy native dependency.

5. Multi-turn tool pattern (most agenty)

Split into exec_start + exec_respond tools. LLM reads prompt output and decides what to type — truly interactive, multiple API round-trips.

Recommendation

Option 1 + 5: non-interactive flags as pragmatic default, multi-turn pattern as the interesting agent-native approach.