feat: add kiro-gateway agent

[ankitcharolia]

Adds kiro-gateway — an ACP-compliant bridge for Kiro that routes all completions through the official `kiro-cli` binary via ACP (JSON-RPC 2.0 over stdio).

What it does

kiro-gateway lets any OpenAI-compatible or Anthropic-compatible AI harness (Cursor, Cline, Claude Code, Kilo Code, OpenCode, Zed, JetBrains, etc.) use a single Kiro subscription by translating between
OpenAI/Anthropic/native ACP APIs and `kiro-cli acp`.

Distribution

• Type: `uvx` (PyPI package)
• Command: `uvx kiro-gateway acp` — speaks ACP (JSON-RPC 2.0) over stdin/stdout
• Auth: Terminal auth via `kiro-cli login` (interactive)

Links

• Repository: https://github.com/ankitcharolia/kiro-gateway
• License: AGPL-3.0-only

Checklist

• `agent.json` with required fields (`id`, `name`, `version`, `description`, `distribution`)
• `icon.svg` — 16×16, monochrome with `currentColor`
• Distribution method: `uvx` with `package` and `args`
• Auth method: `terminal` (delegates to `kiro-cli login`)" 2>&1