Claude sessions' PreToolUse hook runs relay-sessions without the hook subcommand #18

Problem

Every tool call in a local Claude session fails, including built-in tools and relay's MCP tools:

PreToolUse:mcp__relay__fs_list hook error: [<bundle>/Contents/Helpers/relay-sessions]: usage: relay-sessions <service|exec|hook> [flags]

The session starts and lists its tools, but it can't call any of them.

Root cause

cmd/relaysessions/main.go sets ClaudeConfig.HookCommandPath to the bare relay-sessions binary path. ensureHookConfig (internal/sessions/provider/claude_hook.go) writes HookCommandPath into the project's .claude/settings.local.json unchanged. Only the fallback resolveHookCommand() appends hook. So Claude Code runs relay-sessions with no mode argument, and it exits with its usage error.

Fix

Make the configured path produce <abs>/relay-sessions hook: either append the subcommand in ensureHookConfig for a configured path the same way the fallback does, or make the field hold the full command and set it that way in main.go. One of the two, with a single source of truth. Add a failing test first: a Claude session built from the real relay-sessions config writes a hook command ending in hook.

Contract

• ClaudeConfig.HookCommandPath keeps its documented meaning: the absolute path to the relay-sessions binary. cmd/relaysessions/main.go is unchanged.
• internal/sessions/provider/claude_hook.go: one helper builds the command for both paths.

  // hookCommand is C6's hook command for a relay-sessions binary: "<binary> hook".
  func hookCommand(binary string) string

  ensureHookConfig writes hookCommand(p.cfg.HookCommandPath) when the path is set. Otherwise it writes hookCommand(<EvalSymlinks'd os.Executable()>). resolveHookCommand keeps its signature and result, and uses the helper.
• Wire shape unchanged: .claude/settings.local.json → hooks.PreToolUse[0].hooks[0].command == "<abs binary> hook", timeout: 120, matcher: "".
• Tests:
  • New, red first: TestEnsureHookConfig_ConfiguredBinaryPathGetsHookSubcommand. HookCommandPath: "/abs/path/relay-sessions" → command "/abs/path/relay-sessions hook".
  • Existing fixtures that set HookCommandPath to a string already ending in hook (claude_hook_test.go, claude_realspawn_test.go) encode the wrong meaning. They change to the bare binary path, and their assertions on the written command stay the same.
• Files: claude_hook.go (dev), the tests above (test writer).

Tasks

• T1 · Failing repro test and fixture correction [Completed - Verified]
• T2 · Fix ensureHookConfig via hookCommand [Completed - Verified]