#8216: Feat: Add sambanova provider

Added sambanova as a new provider with OpenAI-compatible API <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR adds SambaNova as a new OpenAI-compatible model provider, including onboarding support (interactive + non-interactive), auth profile storage, implicit provider resolution, and documentation updates (provider page + gateway configuration examples). The core integration lives in the onboarding/auth flow (`src/commands/*`) and implicit provider discovery (`src/agents/models-config.providers.ts`), aligning SambaNova with the existing pattern used for other API-key providers like OpenRouter/Venice/Moonshot. <h3>Confidence Score: 2/5</h3> - This PR has multiple correctness issues that will prevent SambaNova from working end-to-end without fixes. - Several typos/mismatches (wrong base URL, malformed model IDs, env key lookup typo, and a stray backtick in a model key) will cause onboarding and implicit provider selection to fail or behave inconsistently. Once corrected, the change should be straightforward. - src/agents/models-config.providers.ts, src/commands/auth-choice.apply.api-providers.ts, src/commands/onboard-auth.config-core.ts, docs/providers/sambanova.md <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->