[FEATURE] Allow skills to clear context before execution

Problem

When starting a new task via a custom skill (e.g. /my-start-task), you typically want a fresh context window — no leftover tokens from the previous conversation polluting the new session.

Currently, the only way to achieve this is to manually type /clear before invoking the skill. This is a minor but constant friction point in daily workflows, especially for skills designed to be session starters.

Proposed Solution

Allow skills to declare that they need a fresh context. Possible approaches:

Option A — Frontmatter flag

---
name: start-task
clear: true
---

When clear: true is set, Claude Code automatically clears the context window before executing the skill.

Option B — Allow hooks to trigger /clear

Let pre-tool hooks (or a new pre-skill hook type) invoke built-in commands like /clear, so users can wire up their own automation.

Option C — Compound commands

Support chaining built-in commands: /clear && /my-skill arg or /clear | /my-skill arg.

Why This Matters

• Skills like "start a new task" are natural session boundaries — they should start clean
• Having to remember /clear before every /start adds friction and is easy to forget
• Forgetting leads to bloated context, hallucinations from stale conversation, and wasted tokens

Current Workaround

/clear
/my-skill my task

Two commands instead of one, every single time.