- Added comprehensive environment variables documentation including API keys for 11 new LLM providers (Groq, Cerebras, xAI, OpenRouter, Mistral, z.ai, MiniMax, OpenCode, Cursor, Vercel AI Gateway, Perplexity) and cloud provider configuration.
- Expanded CLI help text with detailed API keys section documenting all supported LLM providers, cloud providers, search services, and model override configuration variables.
- Fixed redundant fallback check in porting guide example by removing duplicate `Bun.env.HOME` reference.
- Migrated all environment variable access from Node.js `process.env` to Bun runtime `Bun.env` API across the entire codebase.
- Updated 71 files including source code, tests, documentation, and configuration to use Bun's native environment variable API.
- Added comprehensive environment variables documentation in `packages/coding-agent/docs/environment-variables.md` covering 100+ environment variables organized by category.
- Updated CHANGELOG entries to reflect migration from `process.env` to `Bun.env` and environment variable prefix changes (PI_* vs OMP_*).
- Maintained identical behavior and logic across all changes - only the environment variable access method was updated.
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