Deprecate bt setup

[Cedric / ViaDézo1er (viadezo1er)]

Show a message warning about the deprecation of bt setup.

Before:

bt
...
setup        Configure Braintrust setup flows
...

After:

bt
...
setup        Configure Braintrust setup flows (deprecated: use curl -fsSL https://braintrust.dev/wizard/setup.sh | sh)
...

Before:

❯ bt setup


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Braintrust
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After:

❯ bt setup
bt setup has been deprecated, use the command below instead:

    curl -fsSL https://braintrust.dev/wizard/setup.sh | sh



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███      ███
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Braintrust
...

Before:

❯ bt setup -h
Configure Braintrust setup flows

Usage: bt setup [OPTIONS] [COMMAND]
...

After:

❯ bt setup -h
Deprecated: use curl -fsSL https://braintrust.dev/wizard/setup.sh | sh

Configure Braintrust setup flows

Usage: bt setup [OPTIONS] [COMMAND]
...

[github-actions]

Latest downloadable build artifacts for this PR commit b95c0974fc8e:

• Workflow run: https://github.com/braintrustdata/bt/actions/runs/30598465614
• Download all artifacts (GitHub CLI): gh run download 30598465614 --repo braintrustdata/bt
• Installers are published from main automatically. To publish one for a PR branch, run release-canary manually via workflow_dispatch.

Available artifact names

• artifacts-build-global
• artifacts-build-local-aarch64-pc-windows-msvc
• artifacts-build-local-x86_64-pc-windows-msvc
• artifacts-build-local-x86_64-apple-darwin
• artifacts-build-local-x86_64-unknown-linux-gnu
• artifacts-build-local-x86_64-unknown-linux-musl
• artifacts-build-local-aarch64-apple-darwin
• artifacts-build-local-aarch64-unknown-linux-gnu
• artifacts-plan-dist-manifest
• cargo-dist-cache