Add Claude Code support

[srid]

nix-agent-wire already provides a Claude Code module. In addittion to opencode, we can add support running claude-code CLI mirroring the exact things provided for opencode.

Implementation Plan

Key Design Decisions

• Claude Code's API config is env-var-based (not a JSON config file like opencode). Based on the official Juspay jclaude() wrapper, it needs: ANTHROPIC_AUTH_TOKEN, ANTHROPIC_BASE_URL, ANTHROPIC_MODEL, multiple model overrides, timeouts, and feature flags.
• Default model: glm-latest (same as opencode)
• No init variant needed (unlike opencode, claude-code doesn't use a config file for API settings)

Environment Variables (from official jclaude() wrapper)

ANTHROPIC_BASE_URL="https://grid.ai.juspay.net/"
ANTHROPIC_AUTH_TOKEN="$JUSPAY_API_KEY"
ANTHROPIC_MODEL="glm-latest"
ANTHROPIC_SMALL_FAST_MODEL="glm-latest"
CLAUDE_CODE_SUBAGENT_MODEL="glm-latest"
ANTHROPIC_DEFAULT_SONNET_MODEL="glm-latest"
ANTHROPIC_DEFAULT_OPUS_MODEL="glm-latest"
ANTHROPIC_DEFAULT_HAIKU_MODEL="glm-latest"
DISABLE_INTERLEAVED_THINKING=true
API_TIMEOUT_MS=600000
BASH_MAX_TIMEOUT_MS=300000
CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS=1
# Unset conflicting vars
GEMINI_API_KEY=""
GOOGLE_CLOUD_PROJECT=""
GOOGLE_APPLICATION_CREDENTIALS=""
CLAUDE_CODE_USE_VERTEX=""
CLOUD_ML_REGION=""
GOOGLE_VERTEX_PROJECT=""
ANTHROPIC_VERTEX_PROJECT_ID=""

Changes Required

New Files

• claude-code/lib.nix — Shared library with API key check and Juspay env vars
• claude-code/packages/oneclick.nix — Wraps claude-code binary with all Juspay env vars via makeWrapper
• claude-code/modules/default.nix — Home-manager module entry point
• claude-code/modules/home-manager.nix — Sets programs.claude-code.settings.env with Juspay env vars
• test/home-manager-claude-code/test.nix — NixOS VM test for home-manager module
• test/home-manager-claude-code/flake.nix — Test flake
• doc/demo-claude-code/demo.tape — VHS tape for claude-code demo
• doc/demo-claude-code/flake.nix — Demo flake

Modified Files

• flake.nix — Add claude-code to overlay, packages, apps, and homeModules (claude-code, claude-code-with-skills)
• opencode/packages/default.nix — Add claude-code to interactive selector menu
• vira.hs — Add ./test/home-manager-claude-code to CI flakes
• README.md — Document claude-code variants and home-manager modules

Verification

• nix run . -- --version — default package builds
• nix build .#claude-code-oneclick — claude-code oneclick builds
• nix run .#claude-code-oneclick without JUSPAY_API_KEY shows error
• nix run . shows updated selector with claude-code option
• vira ci -b — all NixOS VM tests pass