fix(ai-gateway): prefer Vertex for Claude models

[chrarnoldus]

Summary

• prefer Google Vertex before Bedrock and Anthropic for Claude models
• apply the preferred provider order to Claude Fable models
• update provider-routing unit coverage

Testing

• pnpm --filter web test --runInBand src/lib/ai-gateway/providers/apply-provider-specific-logic.test.ts
• pnpm --filter web lint
• pnpm --filter web typecheck
• git diff --check

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (2 files)

• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.ts
• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.test.ts

Previous Review Summaries (3 snapshots, latest commit 8bb10e8)

Current summary above is authoritative. Previous snapshots are kept for context only.

Previous review (commit 8bb10e8)

Status: No Issues Found | Recommendation: Merge

Files Reviewed (2 files)

• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.ts
• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.test.ts

Previous review (commit 01ea1f5)

Status: No Issues Found | Recommendation: Merge

Files Reviewed (2 files)

• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.ts
• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.test.ts

Previous review (commit e481dd2)

Status: No Issues Found | Recommendation: Merge

Files Reviewed (2 files)

• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.ts
• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.test.ts

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