Implement Baseten chat completions adapter

[Photon101]

Summary

• replace the Baseten stub with its documented OpenAI-compatible chat completions endpoint
• fix the secret key to BASETEN_API_KEY and use Baseten's required Authorization: Api-Key ... scheme
• add model API defaults, self-deployed baseUrl override support, standard generation options, opts.extra passthrough, usage mapping, dry-run behavior, and concise HTTP error handling

Docs used:

• https://docs.baseten.co/reference/inference-api/chat-completions
• https://docs.baseten.co/inference/model-apis/overview

Validation

• corepack pnpm exec vitest run packages/ai/baseten/src/index.test.ts
• corepack pnpm exec tsc -p packages/ai/baseten/tsconfig.json --noEmit
• git diff --check

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[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.