fix: add Pioneer Claude Opus 5 Fast route

[opencode-agent]

Summary

• add Pioneer's currently served claude-opus-5-fast route
• inherit shared Claude Opus 5 metadata
• record Pioneer pricing, reasoning efforts, and reasoning side channel

Evidence

• Pioneer's public model API lists the route as active with text and image inputs
• the API reports a 1,000,000-token input limit, 128,000-token output limit, and $10/$50 per million input/output tokens
• Pioneer metadata exposes low, medium, and high reasoning efforts

Validation

• bun validate
• bun packages/core/script/sync-models.ts pioneer --dry-run --no-issues (0 updates; route no longer reported missing)

Closes #4128

Requested by: @rekram1-node (Aiden via Slack)

[github-actions]

No actionable findings.