Move install and start scripts to run within modules via coder_scripts #698

Summary

This is the second stage of the agentapi module abstraction improvement (#696). The goal is to have install scripts and start scripts run within individual modules via coder_scripts, rather than being orchestrated by the agentapi module.

Current Problem

In the optional agentapi PR (#599), the agentapi module is responsible for running both install and start scripts. This creates tight coupling between modules and makes the logic complex and difficult to maintain when agentapi is optional.

Proposed Solution

1. Modules handle their own scripts: Each module (e.g., claude-code, aider) runs its own install and start scripts via coder_scripts

2. agentapi module's single responsibility: The agentapi module will only be responsible for installing agentapi and running .agentic-module/agent-command.sh when agentapi is enabled

3. Common logic abstraction: Depending on the amount of common logic b/w the coder_scripts, consider abstracting shared functionality to an independent module

Benefits

• Simplified optional agentapi logic: Users can easily toggle agentapi on/off without complex conditional script handling
• Reduced module dependencies: Modules become more self-contained
• Better configuration options: Users get cleaner configuration without hidden dependencies
• Improved maintainability: Clearer separation of concerns compared to the current POC approach

Related

• Parent issue: Improve agentapi module abstraction for configuration and flags #696 (Improve agentapi module abstraction for configuration and flags)
• Optional agentapi PR: feat:(claude-code) optional agentapi #599

Created on behalf of @work-jaykumar