Context

Codex already supports custom binary paths via three resolution tiers:

1. CODEX_BIN_PATH env var
2. assistants.codex.codexBinaryPath in .archon/config.yaml
3. ~/.archon/vendor/codex/<platform-binary> vendor directory

Claude Code has no equivalent. It always uses the SDK-embedded binary via @anthropic-ai/claude-agent-sdk/embed. If a user has Claude Code installed at a non-standard path, there's no way to point Archon at it.

Proposed

Add claudeBinaryPath to ClaudeProviderDefaults and wire it through to pathToClaudeCodeExecutable in the SDK Options, mirroring the Codex pattern:

assistants:
  claude:
    claudeBinaryPath: /usr/local/bin/claude  # Optional: custom Claude Code binary

Plus CLAUDE_BIN_PATH env var as the highest-precedence override.

Priority

Low — the SDK bundles its own binary, so this hasn't been a real problem yet. But for consistency with Codex and for users with non-standard setups, it's worth having.