Add opt-in Rich and OpenTelemetry integrations

[codeforester]

Parent: #50

Train position: 16 of 22
Phase: P2 — Operational completeness

Problem

Adopters need polished interactive rendering and standard telemetry without increasing the core dependency or failure surface.

Acceptance criteria

• Separate optional extras add no core import-time or runtime dependency.
• Rich enhances human rendering while preserving redirected and machine-readable contracts.
• OpenTelemetry emits lifecycle spans/events with run ID, outcome, duration, and safe attributes without raw secrets.
• Missing or broken exporters never break command completion.
• Documentation and integration tests cover installation, enable/disable behavior, and graceful degradation.

Dependencies

• Define stable structured-log, JSON output, and JSON error contracts #63
• Stream delimited output and render terminal-aware tables #65