[Feature Request] Configurable plan storage location and naming convention

Feature Request Description
Currently, plan files are stored in ~/.claude/plans/ with auto-generated names (e.g., jaunty-petting-nebula.md). I'd like to configure:

1. Location: Store plans in a project-local folder (e.g., ./specs/) so they can be version-controlled with the project
2. Naming convention: Custom pattern like 2025-<feature-name>-plan.md instead of random adjective combinations

Suggested settings.json config:
{
"plans": {
"directory": "./specs",
"namePattern": "2025-{feature}-plan.md"
}
}

Why: Plans are valuable project artifacts that should live with the codebase, not in a global folder. This enables code review of plans, historical tracking, and team
collaboration.

Environment Info

• Platform: darwin
• Terminal: Apple_Terminal
• Version: 2.0.62
• Feedback ID: 7cea353c-2f8c-4dca-84fd-5f0ca37d084d

Errors

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