pr-review-toolkit: silent-failure-hunter agent has invalid YAML frontmatter, loads with empty metadata

Summary

plugins/pr-review-toolkit/agents/silent-failure-hunter.md has invalid YAML frontmatter. The agent loads with empty metadata — every frontmatter field (name, description, model, color) is silently dropped at runtime.

The other 5 agents in the same plugin parse fine.

Root cause

The description value is unquoted and contains embedded : sequences inside the example dialogue:

Daisy: "I've added error handling to the API client. Can you review it?"
Assistant: "Let me use the silent-failure-hunter agent..."

In YAML, key: value inside an unquoted scalar is parsed as a nested mapping, which is invalid in that position.

Reproduction

git clone --depth 1 https://github.com/anthropics/claude-code
python3 - <<'PY'
import re, yaml
p = "claude-code/plugins/pr-review-toolkit/agents/silent-failure-hunter.md"
fm = re.match(r'^---\n(.*?)\n---\n', open(p, encoding='utf-8').read(), re.S).group(1)
yaml.safe_load(fm)
PY

Result:

yaml.scanner.ScannerError: mapping values are not allowed here
  in "<unicode string>", line 2, column 393

claude plugin validate reports the same, and states the runtime consequence explicitly:

❯ frontmatter: YAML frontmatter failed to parse: YAML Parse error: Unexpected token.
  At runtime this agent loads with empty metadata (all frontmatter fields silently dropped).

Impact

The agent cannot be selected by description-based routing, since its description never reaches the model. Users installing pr-review-toolkit get 5 working agents out of 6, with no error surfaced unless they run claude plugin validate manually.

Suggested fix

Quote the description as a YAML block scalar, matching what code-simplifier.md in the same plugin already does:

description: |
  Use this agent when reviewing code changes in a pull request to identify
  silent failures, inadequate error handling, and inappropriate fallback behavior.
  ...

Environment

• Found via claude plugin validate on an installed copy, then confirmed against a fresh clone of main
• Also affects the mirrored copy distributed through the claude-plugins-official marketplace