fix(shell): drain stdout/stderr to prevent command hanging on large output

[konard]

Problem

pnpm run docker-git clone <repo> --force --mcp-playwright hangs indefinitely and never completes.

Root Cause

In packages/lib/src/shell/command-runner.ts, both runCommandExitCode and runCommandCapture start child processes with "pipe" mode for stdout/stderr but do not drain those streams. The OS pipe buffer is typically ~64 KB. When a sub-command (e.g. git push or git stash pop during autoSyncState after a successful clone) writes more than that to stdout or stderr, the child process blocks waiting for the buffer to drain — and since nobody is reading it, it hangs forever.

Fix

runCommandExitCode

Rewrote from a simple Effect.map(Command.exitCode(...), Number) to an Effect.scoped block that:

1. Manually starts the process via executor.start
2. Forks daemon fibers to drain bothprocess.stdout and process.stderr concurrently
3. Awaits process.exitCode

runCommandCapture

Added yield* _(Effect.forkDaemon(Stream.runDrain(process.stderr))) before collecting stdout, so large stderr output no longer causes a deadlock.

Mathematical Guarantees

Invariants

• ∀ cmd: runCommandExitCode(cmd) terminates iff cmd terminates (no buffer deadlock)
• ∀ cmd: runCommandCapture(cmd) terminates iff cmd terminates

Preconditions

• Command process started with "pipe" for stdout, stderr, stdin

Postconditions

• runCommandExitCode: returns numeric exit code, stdout/stderr fully consumed
• runCommandCapture: returns decoded stdout string, stderr fully consumed, exit code validated

Test plan

• Run pnpm run docker-git clone <repo> --force --mcp-playwright and verify it completes without hanging
• CI checks pass (Build, Types, Lint, Test, E2E)

🤖 Generated with Claude Code

Fixes#153

[konard]

🤖 Solution Draft Log

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💰 Cost estimation:

• Public pricing estimate: $0.324257
• Calculated by Anthropic: $0.420490 USD
• Difference: $0.096234 (+29.68%)

🤖 Models used:

• Tool: Claude
• Requested: sonnet
• Main model: Claude Sonnet 4.6 (ID: claude-sonnet-4-6, Anthropic, cutoff: 2025-08)
  📎 Log file uploaded as Gist (401KB)
  🔗 View complete solution draft log

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[konard]

✅ Ready to merge

This pull request is now ready to be merged:

• All CI checks have passed
• No merge conflicts
• No pending changes

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