feat(agents): add Nexus Code agent

Adds Nexus Code, an open-source local coding agent CLI, as a supported agent.

Nexus loads SKILL.md skills from ./.agents/skills and ~/.agents/skills. Project skills load only when the workspace is trusted. Nexus follows symlinked skill directories and parses YAML block-scalar descriptions. The .agents/skills loading is in mikeholownych/nexus-code#397, and the linked docs page describes these directories once that PR merges. Because Nexus uses the canonical directory, no agent-specific symlinks are created for it.

Changes

• src/agents.ts, src/types.ts: the agent entry.
• README.md, docs/agents.md, package.json keywords: regenerated with scripts/sync-agents.ts.
• tests/nexus-paths.test.ts: covers registry fields, universal membership, and project/global base dirs.
• .changeset/add-nexus-code-agent.md: patch.

Verification

• node scripts/validate-agents.ts: all agents valid.

• pnpm format:check, pnpm type-check and pnpm build pass.

• pnpm test: the new tests pass. On the same machine, the failing tests on this branch are a subset of those failing on the base commit (92a9a34). The failures that remain come from that machine:

  • XDG_CONFIG_HOME was set;
  • the run happened inside an agent session (detect-agent);
  • update tests need network access.

  Running the XDG and detect-agent tests with env -i clears those failures.

• End to end with an isolated HOME:

  • add <local> --agent nexus -y, for both project and -g installs.
  • list --agent nexus and remove --agent nexus.
  • add vercel-labs/agent-skills --agent nexus --skill '*' installed 9 skills, and add anthropics/skills --agent nexus --skill '*' installed 20. Nexus then loaded every installed skill.

🤖 Generated with Claude Code