Refresh installer CLI UI: purple theme, cleaner layout, better CX

[anirudha]

Description

Refreshes the CLI installer UI for a cleaner, more customer-focused experience. Replaces fragile box-drawing borders (which broke across terminal widths and emoji rendering) with simple, reliable text formatting. Reorients the completion summary around the two things users care about most: where the UI is and where to send data.

Changes

Color theme - Purple

• Step arrows and spinners changed from blue/cyan to purple
• Header title in purple
• Next Steps section and URLs highlighted in purple
• Green retained for success indicators, completed arrows
• Red available for errors

Header (before)

╔════════════════════════════════════════════════════════════╗
║              Observability Stack Installer v0.1            ║
║            Open-source Agent Observability                 ║
╚════════════════════════════════════════════════════════════╝

Header (after)

  Observability Stack

  Installer v0.1
  Agents, Services, Logs, Metrics, Traces & Evals

Completion summary (after)

• Observability Stack Install Complete!
• UI endpoint highlighted first with inline credentials
• Send OTLP endpoint (gRPC + HTTP) highlighted second
• Other services dimmed as secondary info
• Next Steps calls out Dashboards URL, OTLP endpoints, and https://opensearch.org/platform/observability/

Why

• Box-drawing characters broke in terminals due to emoji double-width rendering
• Previous layout treated all endpoints equally - customers need UI and OTLP front and center
• Tagline updated from Open-source Agent Observability to Agents, Services, Logs, Metrics, Traces and Evals
• Link to opensearch.org/platform/observability/ replaces local examples path in Next Steps

Testing

bash demo-install.sh

Verified clean rendering with no broken borders in macOS terminal.