[FEATURE] #879 - Add multi-agent CLI tool selection and role-based dispatch

[stephanj]

Parent Issue

Part of #879 — Support Multi-Agent Execution Modes Per Task

Context

CliTaskExecutorService currently dispatches to a single CLI tool per task (the one selected in settings). Multi-agent modes require dispatching different phases to different tools — e.g., Claude as implementer, Copilot as reviewer. The existing CliToolConfig model supports multiple enabled tools but only one is used per task.

Task

Enable role-based CLI tool selection so different agents can use different tools.

Key Changes

1. Extend Agent settings with role-to-tool mapping:

   • Default implementer tool (dropdown of enabled CLI tools)
   • Default reviewer tool (dropdown of enabled CLI tools)
   • Default validator tool (dropdown or "same as implementer")
   • Allow different tools per role (e.g., Claude implements, Gemini reviews)

2. Add resolveToolForRole(AgentRole role) to settings:

   CliToolConfig resolveToolForRole(AgentRole role) {
       return switch (role) {
           case IMPLEMENTER -> getImplementerTool();
           case REVIEWER -> getReviewerTool();
           case VALIDATOR -> getValidatorTool();
       };
   }

3. Update MultiAgentPhaseManager to call resolveToolForRole() before each phase dispatch.

4. Update CliTaskExecutorService.execute() to accept role-specific CliToolConfig (already parameterized — just ensure the phase manager passes the right config).

5. LLM mode equivalent: For LLM-mode execution, allow different models per role (e.g., Opus for implementation, Sonnet for review).

Files to Modify

• src/main/java/com/devoxx/genie/ui/settings/agent/AgentSettingsComponent.java
• src/main/java/com/devoxx/genie/service/DevoxxGenieSettingsService.java
• src/main/java/com/devoxx/genie/service/spec/MultiAgentPhaseManager.java

Dependencies

• Requires: TaskExecutionMode enum ([FEATURE] #879 - Add TaskExecutionMode enum and per-task configuration #902)
• Requires: MultiAgentPhaseManager ([FEATURE] #879 - Implement MultiAgentPhaseManager for orchestrating agent sequences #904)

Acceptance Criteria

• Settings UI allows selecting different CLI tools per agent role
• resolveToolForRole() returns correct tool for each role
• Implementer and reviewer can use different CLI tools in the same task
• Default: all roles use the same tool (backward compatible)
• Settings persist across IDE restarts