docs: update skill.md to sei-docs developer reference

[monty-sei]

Replaces the old sei-network skill with the new sei-docs developer reference playbook from sei-protocol/sei-skill. Covers critical Sei facts, networks, default stack, MCP server, precompile addresses, quick start, key doc links, RPC agent skills, and agent safety patterns.

[cursor]

PR Summary

Low Risk
Low risk documentation-only change; main risk is correctness/maintenance of hardcoded chain parameters, RPC URLs, and gas guidance that may drift from current network values.

Overview
Updates skill.md from an RPC-execution oriented sei-network skill into a non-user-invocable sei-docs developer reference for docs.sei.io, including refreshed metadata and positioning.

Replaces the previous per-skill API descriptions with curated guidance: critical Sei EVM facts (finality, gas model, chain IDs), network/RPC tables, an opinionated tooling stack, MCP server setup, precompile address list, quickstart snippets, key doc links, and standardized agent safety + write-operation flow patterns for RPC-based interactions.

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Project	Status	Preview	Updated (UTC)
sei-docs	🟢 Ready	View Preview	May 21, 2026, 12:11 AM