Add environments field support to pull function

[Parker Henderson (parkerhendo)]

TL;DR

Added support for environments field in prompt configurations with automatic slug normalization.

What changed?

• Added environments field to PullFunctionRow and NormalizedPrompt structs
• Implemented normalize_environment_slugs function that extracts slug values from environment objects or accepts string values directly
• Added environments rendering support for both TypeScript and Python project file generation
• Environments are normalized to arrays of string slugs, filtering out empty values and trimming whitespace

How to test?

• Create prompts with environments configured as objects with slug fields or as string arrays
• Run the pull command and verify that environments are properly rendered in generated TypeScript and Python files
• Test that empty slugs and whitespace are properly handled during normalization

Why make this change?

This enables prompts to specify which environments they should be available in, providing better organization and deployment control for prompt configurations across different runtime environments.

[github-actions]

Latest downloadable build artifacts for this PR commit 9a81f27a8ff5:

• Workflow run: https://github.com/braintrustdata/bt/actions/runs/24110137831
• Download all artifacts (GitHub CLI): gh run download 24110137831 --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-x86_64-apple-darwin
• ``artifacts-build-local-x86_64-pc-windows-msvc
• ``artifacts-build-local-x86_64-unknown-linux-musl
• ``artifacts-build-local-x86_64-unknown-linux-gnu
• ``artifacts-build-local-aarch64-unknown-linux-musl
• ``artifacts-build-local-aarch64-unknown-linux-gnu
• ``artifacts-build-local-aarch64-apple-darwin
• ``artifacts-plan-dist-manifest
• ``cargo-dist-cache