Restrict code review agent from approving or rejecting PRs

Changed agent tool declaration from `Bash(gh pr review:*)` to
`Bash(gh pr review:--comment*)` to explicitly prevent the agent
from executing PR approval or rejection operations.

This closes a permission gap where the wildcard pattern technically
allowed `--approve` and `--request-changes` flags, though the agent
was never instructed to use them. The agent retains full ability to
post inline review comments and summary comments.

Security hardening following principle of least privilege.

.github/workflows/_review-code.yml

@@ -137,4 +137,4 @@ jobs:
             Do not add excessive praise or commentary to findings.
           claude_args: |
             --verbose
-            --allowedTools "Read,Grep,Glob,Bash(git diff:*),Bash(git log:*),Bash(git show:*),Bash(gh pr view:*),Bash(gh pr diff:*),Bash(gh pr review:*),Bash(gh pr comment:*),mcp__github_comment__update_claude_comment,mcp__github_inline_comment__create_inline_comment"
+            --allowedTools "Read,Grep,Glob,Bash(git diff:*),Bash(git log:*),Bash(git show:*),Bash(gh pr view:*),Bash(gh pr diff:*),Bash(gh pr review:--comment*),Bash(gh pr comment:*),mcp__github_comment__update_claude_comment,mcp__github_inline_comment__create_inline_comment"