security: gate command DSL health checks on isEmbedded

[garagon]

Summary

gbrain integrations doctor runs health checks from recipe YAML files. In v0.9.3,
a typed DSL was added with 4 check types: http, env_exists, command, and any_of.
The command type runs a binary via spawnSync.

The problem: recipes can be loaded from recipes/ in the current working directory.
The old string-based health checks had an isUnsafeHealthCheck() guard for non-embedded
recipes, but the new command DSL type skips that check entirely. A malicious recipe
in CWD with a command health check executes arbitrary binaries on gbrain integrations doctor.

What the fix does

Before calling spawnSync, the handler checks isEmbedded. If the recipe is NOT
first-party (loaded from CWD), the command check returns status: 'blocked' without
executing anything. First-party recipes continue to work as before.

Changes

src/commands/integrations.ts

• isEmbedded gate at the top of the command case, before spawnSync

test/integrations.test.ts

• New test: command check with isEmbedded=false returns blocked
• Existing command tests (exit 0 ok, exit 1 fail) still pass with isEmbedded=true

Validation

• bun test test/integrations.test.ts — 38 pass, 0 fail