feat(ai-gateway): add discounted Claude Opus 4.8 stealth model

[kilo-code-bot]

Summary

• Adds a discounted (stealth) Claude Opus 4.8 model mirroring the existing Opus 4.7 stealth model, offered at 20% off standard Opus 4.8 pricing via the martian gateway.
• Registers the new model in kiloExclusiveModels and preferredModels.

Verification

• Reviewed that the new claude_opus_4_8_stealth_model follows the same shape/flags/pricing as claude_opus_4_7_stealth_model.

Visual Changes

N/A

Reviewer Notes

• Pricing reuses CLAUDE_OPUS_STEALTH_PRICING (4 / 20 / 0.4 / 5), same as the 4.7 variant. Adjust if Opus 4.8 discounted pricing should differ.
• internal_id set to anthropic/claude-opus-4-8:optimized; confirm this matches the gateway's expected upstream id.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Executive Summary

The PR cleanly adds a new claude_opus_4_8_stealth_model entry following the exact same pattern as the existing claude_opus_4_7_stealth_model, with consistent internal_id formatting, correct placement in preferredModels and kiloExclusiveModels, and appropriate flags.

Files Reviewed (2 files)

• apps/web/src/lib/ai-gateway/providers/anthropic.constants.ts
• apps/web/src/lib/ai-gateway/models.ts

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Fix issues in Kilo Cloud

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_{Reviewed by claude-sonnet-4.6 · 309,254 tokens}

_{Review guidance: REVIEW.md from base branch main}