fix: add policy pull command

[Mr-Lucky]

Summary

Fixes #71.

This adds the missing agentguard policy pull command referenced by AgentGuard Cloud's runtime policy refresh instructions.

Changes

• Add agentguard policy pull under the CLI policy command group.
• Fetch the latest effective runtime policy from /api/v1/policies/effective.
• Save the pulled policy to the configured local policy cache path.
• Add --json output for automation-friendly usage.
• Add a CLI regression test covering policy pull and cache writes.
• Document the fix under Unreleased.

Type

• [✅] Bug fix
• New feature / detection rule
• Refactoring
• Documentation

Testing

• [✅] npm run build passes
• [✅] npm test passes (32 tests)
• Manually tested the change

Related Issues

Closes #71

[github-actions]

AgentGuard PR Review

This patch adds a new policy pull command, but there are a couple of concrete issues that could break behavior or weaken security.

1. medium — src/cli.ts (policy pull command): no validation of the fetched policy before caching

   • What can go wrong: The command writes whatever fetchEffectivePolicy() returns directly to the local cache. If the cloud endpoint is misconfigured, compromised, or returns malformed/malicious policy data, the CLI will persist it and downstream agents may apply unsafe rules.
   • Fix suggestion: Validate the response against the runtime policy schema before calling saveCachedPolicy(), and reject/exit non-zero on schema violations.

2. medium — src/tests/cli-policy.test.ts: test only exercises the happy path and can miss build/runtime regressions in the new CLI flow

   • What can go wrong: The new command depends on dist/cli.js, but the test never verifies behavior when the cache path is unwritable, the cloud returns invalid JSON, or connected is false. A regression in those paths could ship unnoticed, including cases where the CLI exits success after a partial failure.
   • Fix suggestion: Add tests for failure cases: disconnected config, non-200 response, invalid policy payload, and unwritable cache path, asserting non-zero exit codes and that no cache file is written.