fix(code-review): include CLAUDE.md agents in step 5 validation

[kpatel513]

Summary

Step 5 validated issues from agents 3 and 4 only, silently dropping all issues flagged by the CLAUDE.md compliance agents (1 and 2). Since step 6 filters out anything not validated in step 5, CLAUDE.md violations were never surfacing in the output — making the compliance review effectively a no-op.

Change

plugins/code-review/commands/code-review.md

• Remove "by agents 3 and 4" scope restriction from step 5 so all four agents' issues go through validation before filtering

Before / After

Before:

For each issue found in the previous step by agents 3 and 4, launch parallel subagents to validate the issue.

After:

For each issue found in the previous step, launch parallel subagents to validate the issue.

Test plan

• Run a review on a PR that violates a CLAUDE.md rule — violation should now appear in output
• Confirm step 5 still uses Opus subagents for bugs and Sonnet subagents for CLAUDE.md violations (unchanged)