feat(pipeline): implement Golden Chain for Cloud Dev — tri cloud pipeline (#140)

Implements Phase 1 of the Golden Chain pipeline with full automation:

New Commands:
- tri cloud pipeline <issue> — Full automation: spawn → monitor → verify → merge → cleanup
- tri cloud verify <issue> — Verify PR locally (zig build)
- tri cloud merge <issue> — Merge PR for issue

Pipeline Features:
- Automatic agent spawning via Railway API
- Heartbeat monitoring with JSONL event streaming
- Stuck detection (>10min without progress) with auto-respawn
- Max 3 retry loops per issue before escalating to human
- PR verification via local zig build
- Auto-merge of verified PRs
- Automatic container cleanup

Enhancements:
- tri cloud agents now shows health indicators (OK/SLOW/STUCK)
- Displays elapsed time in human-readable format (XmYs)
- Tracks stuck agents (>10min) separately
- Real-time dashboard with status emojis and color coding

Exit Criteria:
- tri cloud pipeline 999 spawns agent, monitors, verifies, merges, cleans up
- Zero human intervention for simple issues
- Max 3 auto-retries before escalating to human

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Trinity Agent