fix: use kiro-cli-chat directly to prevent orphan child processes

[vokako]

Problem

kiro-cli is a wrapper that forks kiro-cli-chat as the actual ACP server process. When acpx sends SIGTERM to kiro-cli on session close, only the wrapper is killed — the child process kiro-cli-chat continues running as an orphan.

These orphaned processes accumulate over time and cause resource conflicts, resulting in ACP_TURN_FAILED errors (exit code 1) on subsequent messages in persistent sessions. The first message in a session works fine, but follow-up messages fail because the stale kiro-cli-chat process is still holding resources.

Fix

Point the built-in kiro agent directly at kiro-cli-chat acp, bypassing the wrapper entirely. This ensures clean process lifecycle management without needing process group kill logic.

One-line change in src/agent-registry.ts:

-  kiro: "kiro-cli acp",
+  kiro: "kiro-cli-chat acp",

Related

• feat: add Kiro CLI as built-in agent with proper process group cleanup #42 proposed a more complex fix using process group cleanup (detached:true + process.kill(-pgid)). This PR provides a simpler alternative that avoids the wrapper entirely.

Testing

• Created persistent kiro session with acpx kiro sessions new
• Sent multiple consecutive messages — all succeeded with session reuse
• Verified only 1 kiro-cli-chat acp process running (no orphans)
• Previously: 6+ orphan processes accumulated after a few session cycles