upgrade instruction to subagent or skill

context: current instruction to LLM is a single custom rule file.
subagent and Claude Skills pros:

### The Core Principle
**Attention Conservation:** LLMs get stupider as context length grows. Modularizing rules stops the AI from "forgetting" instructions by never loading irrelevant ones in the first place.

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### Part 1: Claude Code Skills (The "Tools")
*Focus: Execution & Specificity*

* **Just-in-Time Context Loading**
* **The Advantage:** Instead of force-feeding the AI 5,000 tokens of rules for every language you use, it loads specific instructions *only* when triggered (e.g., only load "AWS Best Practices" when you type `deploy`).
* **Result:** Saves token costs and keeps the AI’s "IQ" higher by reducing distraction.
* **Deterministic Reality (Fact vs. Hallucination)**
* **The Advantage:** A text rule asks the AI to "guess" the state of your code. A Skill (via MCP) runs a command (like `grep` or `linter`) to *verify* the state.
* **Result:** Moves the agent from "I think this is broken" to "I have executed code and confirmed this is broken."
* **Encapsulated Logic**
* **The Advantage:** You can treat prompts like software functions. You can fix the logic for a "Database Migration" skill without accidentally breaking the logic for a "Frontend Component" skill.

### Part 2: Subagents (The "Specialists")
*Focus: Reasoning & Context Hygiene*

* **Context Hygiene (The "Fresh Start")**
* **The Advantage:** Subagents spin up a brand new context window. They do not see your previous 40 messages of debugging errors.
* **Result:** They solve the immediate problem with zero bias or "confusion hangover" from previous failed attempts.
* **Role Specialization**
* **The Advantage:** A single `.cursorrules` file tries to make one model a Jack-of-all-trades. Subagents allow you to configure one model purely as a "Hostile Security Reviewer" and another as a "Helpful UI Designer."
* **Result:** You get depth of expertise rather than shallow breadth.
* **Parallelization**
* **The Advantage:** You can have a "Doc Writer" agent and a "Unit Test" agent working simultaneously on the same code block.
* **Result:** Faster wall-clock time for complex tasks, though this is harder to orchestrate.

### The Honest Trade-off
* **Single File:** Fast, stupid, easy to manage. Best for quick scripts.
* **Skills/Subagents:** Slower, smarter, harder to maintain. Required for enterprise-grade engineering.