feat: add TerminalProgressGroup component

[clawgreen]

What does this PR do?

Adds a new TerminalProgressGroup component for displaying multiple related progress bars (multi-step tasks like build pipelines, installations, deployments).

Features

• Multiple progress bars: Group related steps together
• Overall progress: Automatic calculation (average of all items)
• Status indicators: ○ pending, ⟳ active, ✓ complete, ✗ error
• Collapsible details: Optional expand/collapse functionality
• Smart colors: Auto-selects variant based on status
• Reuses TerminalProgress: Built on existing component

Example Usage

<TerminalProgressGroup
  title="Build Pipeline"
  items={[
    { label: "Compile TypeScript", percent: 100, status: "complete" },
    { label: "Bundle assets", percent: 75, status: "active", variant: "blue" },
    { label: "Deploy to prod", percent: 0, status: "pending" },
  ]}
/>

// Collapsible variant
<TerminalProgressGroup
  title="Deployment"
  collapsible
  items={[...]}
/>

Type of Change

• 📦 New component
• ✨ Enhancement (playground examples)

Checklist

• Component created in components/terminal-progress-group.tsx
• TypeScript interfaces with JSDoc
• Exported from components/terminal.tsx
• Playground examples (normal + collapsible)
• Build passes (pnpm run build)
• Follows project patterns
• Zero new dependencies

Screenshots

See playground at /playground for live examples of build pipeline and deployment scenarios.

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Part of NEW_COMPONENTS_PLAN.md (Phase 2)

[vercel]

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