Use AGENTS.md as Kilo Code rules output

[Copilot]

Issue summary: Kilo Code should consume rules from AGENTS.md instead of the legacy .kilocode/rules path to align with standard agent outputs. This updates the agent behavior and references accordingly.

• Kilo Code behavior: write rules to root AGENTS.md using the standard generated marker while preserving MCP/skills support.
• Docs & tests: refresh README and Kilo Code-related tests to reflect the AGENTS.md output.

Example (updated default output path):

export class KiloCodeAgent extends AgentsMdAgent {
  getDefaultOutputPath(projectRoot: string): string {
    return path.join(projectRoot, 'AGENTS.md');
  }
}

Original prompt

Implement #133 by getting the Kilo Code agent so use AGENTS.md for rules

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