docs: add prerequisites section for utility script dependencies

- README.md: Add "For Utility Scripts" section documenting jq, grep, sed requirements
- hook-development/SKILL.md: Add prerequisites note referencing main README

Verified that scripts use bash 3.2+ features only (regex matching), not bash 4.0+.

Fixes #152

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: sjnims

README.md

@@ -42,10 +42,32 @@ Each component follows progressive disclosure: lean core documentation with deta
 
 ## Prerequisites
 
+### Required
+
 - [Claude Code CLI](https://docs.anthropic.com/en/docs/claude-code) installed and configured
-- Bash shell (for utility scripts)
 - Git (for version control and marketplace publishing)
 
+### For Utility Scripts
+
+The plugin includes utility scripts for validation and testing. These require:
+
+| Tool | Version | Purpose |
+|------|---------|---------|
+| bash | 3.2+ | Shell scripting (macOS default works) |
+| jq | 1.6+ | JSON parsing and validation |
+| grep | - | Pattern matching (with `-E` support) |
+| sed | - | Stream editing (GNU or BSD) |
+
+**Check your environment:**
+
+```bash
+bash --version | head -1
+jq --version
+grep --version 2>&1 | head -1
+```
+
+> **Note**: `jq` may need to be installed. macOS: `brew install jq`, Linux: `apt install jq`
+
 ## Installation
 
 Add this marketplace and install the plugin:

plugins/plugin-dev/skills/hook-development/SKILL.md

@@ -695,6 +695,8 @@ Working examples in `examples/`:
 
 ### Utility Scripts
 
+> **Prerequisites**: These scripts require `jq` for JSON validation. See the [main README](../../../../README.md#for-utility-scripts) for setup.
+
 Development tools in `scripts/`:
 
 - **`validate-hook-schema.sh`** - Validate hooks.json structure and syntax