… keywords)

Replace keyword-based skill auto-injection with a code-enforced gate that
leverages the LLM's own semantic understanding to select relevant skills.

How it works:
1. System prompt includes all skill names + descriptions (existing mechanism)
2. A mandatory instruction tells the agent to evaluate skills before acting
3. A pre_tool_call hook BLOCKS non-read tools until skill_view() is called
4. After skill_view() is called once, the gate opens for the rest of the session

This is universal (works for any language), lightweight (no extra API calls),
and code-enforced (agent cannot skip it). No keyword matching.

Changes:
- agent/skill_eval_gate.py: New module with gate logic and instruction text
- run_agent.py: Integrate gate into system prompt + both tool dispatch paths