[FEATURE] expand ${CLAUDE_PLUGIN_ROOT} in "allowed-tools" portion of skills

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

The YAML preamble for skills could be a lot more flexible in supporting skill scripts if it expanded this env variable, allowing skill authors to whitelist skill scripts.

Proposed Solution

This would now work, where the update script is part of the skill:

allowed-tools: allowed-tools: Bash(python3 ${CLAUDE_PLUGIN_ROOT}/scripts/update_docs_cache.py)

If you elect to NOT support this feature, then at least issue a diagnostic if env vars are detected in allowed-tools

Alternative Solutions

_No response_

Priority

High - Significant impact on productivity

Feature Category

Developer tools/SDK

Use Case Example

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Additional Context

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