Add SambaNova provider catalog

[rekram1-node]

Summary

• add SambaNova as an OpenAI-compatible provider
• catalog all 6 models returned by the official live SambaCloud /v1/models endpoint on 2026-06-10
• reconcile the 2026-06-09 preview removals and provider-specific reasoning controls

Audit

• active models: 6 total (4 production, 2 preview)
• reasoning: DeepSeek-V3.1 fixed/unspecified control, DeepSeek-V3.2 toggle, gpt-oss-120b low/medium/high effort
• non-reasoning conservatively recorded where SambaNova-specific reasoning behavior was not established: MiniMax-M2.7, gemma-4-31B-it, Meta-Llama-3.3-70B-Instruct
• no authenticated probes were run because SAMBANOVA_API_KEY was unavailable; the official unauthenticated model metadata endpoint was queried successfully

Validation

• bun validate
• git diff --check
• bun test packages/core/test/generate.test.ts (9/10 pass; only the pre-existing repository-wide missing weights-link inventory fails, listing unrelated Sarvam/NVIDIA/Cohere models)