[Feature]: Make Sisyphus available as a CLI agent

[manascb1344]

Add Sisyphus as an invokable agent in oh-my-opencode for CLI usage.

Problem Description
Sisyphus is the primary orchestrating agent but is not available as a subagent for CLI commands like opencode run --agent sisyphus or opencode agent run sisyphus. Users must use the TUI mode (opencode) to access Sisyphus functionality.

Proposed Solution

• Add 'sisyphus' to the agent list.
• Allow CLI invocation with delegation capabilities.
• Support custom model configuration like other agents.

Additional Context
This would enable CLI-based orchestration without requiring TUI mode.

[manascb1344]

Right now when we use opencode run, it defaults to build agent even if oh my opencode plugin is installed