install: SubagentStart reminder points agents without MCP tools at tools they don't have #2837

Summary

The SubagentStart context tells every subagent to use search_graph / trace_path / get_code_snippet. Many agent types are defined with an explicit tool list that has no MCP tools (e.g. tools: Read, Grep, Glob, Bash). Those agents can still use the graph through codebase-memory-mcp cli <tool>, but the reminder never says so, so they either ignore it or try tools they don't have.

Details

The installed SubagentStart hook uses matcher "*" (src/cli/cli.c:6320-6365, cbm_upsert_claude_subagent_hooks_with_binary). Claude Code's SubagentStart input carries agent_type and agent_id but not the agent's tool list, and hook_augment.c:1642 already reads agent_type (only to choose a tier). Proposed fix (PR to follow): since the hook can't know the tool list, add one sentence to the Subagent context: when the mcp__codebase-memory-mcp__* tools are not available, run the same tools through codebase-memory-mcp cli <tool> --help / cli <tool> --flag value. That works for every agent type with no detection.

Alternatives considered: (a) settings only: SubagentStart matchers are JS regexes, so the installer could write a negative lookahead such as ^(?!statusline-setup$|claude-code-guide$).* instead of "*". Fuller option: in the hook, resolve agent_type to its definition (.claude/agents/*.md, ~/.claude/agents/*.md) and, when its tools: frontmatter is an explicit list without mcp__codebase-memory-mcp__*, emit CLI-form guidance (codebase-memory-mcp cli search_graph …) instead of MCP tool names. Built-in types with restricted tools (e.g. statusline-setup) can be a small static skip-list.

Investigated and written by Claude Opus 5.5 (Anthropic) in Claude Code, at the request of @halindrome.