feat(pool): add Pool CLI module

[ausbru87]

Summary

• add a coder-labs/pool module to install and configure Poolside's Pool CLI
• support direct Poolside credentials/deployment API URLs and generic OpenAI-compatible endpoints
• add Coder AI Gateway support using the workspace owner's session token and the OpenAI-compatible gateway endpoint
• include Terraform tests, docs, and a Poolside icon

Validation

• terraform fmt -check -diff registry/coder-labs/modules/pool
• terraform test -no-color (7 passed)

Implementation plan

1. Model the module structure and script orchestration after the existing Claude Code and Codex modules.
2. Install Pool noninteractively using Poolside's official installer, accepting the EULA and exposing the binary through Coder and shell paths.
3. Expose direct API and OpenAI-compatible endpoint settings through Pool's documented environment variables.
4. For AI Gateway, set POOLSIDE_STANDALONE_BASE_URL to Coder's OpenAI-compatible gateway endpoint and POOLSIDE_API_KEY to the workspace owner's session token; reject conflicting direct endpoint/key inputs at plan time.
5. Document all modes and add native Terraform tests for defaults, direct credentials, standalone endpoints, AI Gateway, validations, and pipeline output ordering.

Generated by Coder Agents.