Custom subagents cannot access MCP tools due to Claude Code bug #13898.
This affects gsd-phase-researcher, gsd-project-researcher, and gsd-planner
which need Context7 for documentation lookups.
Fix: Switch to general-purpose agent (which has MCP access) and have it
read the agent instruction file as its first action. The specialized
behavior comes from the prompt, not the agent definition.
Closes#161
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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