Fix top-level await in skill code examples

[marc0olo]

Context

Identified in #95 (comment): the build.target: "esnext" recommendation proposed in #95 is unnecessary. The real issue is that skill code examples use bare top-level await, which fails with Vite's default build target (es2020).

Problem

Three skills have await at module scope in their code blocks. When an agent copies these into a Vite-bundled module, the build fails with "Top-level await is not available in the configured target environment".

Affected skills:

• internet-identity/SKILL.md — await AuthClient.create(), await authClient.isAuthenticated()
• wallet-integration/SKILL.md — await IcrcWallet.connect(...)
• asset-canister/SKILL.md — await HttpAgent.create(...)

Fix

Wrap all top-level await examples in async functions:

async function init() {
  const authClient = await AuthClient.create();
  // ...rest of auth flow
}
init();

This works with any Vite build target and is more realistic — real apps initialize inside lifecycle hooks or init functions, not at module scope.

Acceptance criteria

• All await in code blocks across the three skills are inside functions
• npm run validate passes
• No build.target: "esnext" added anywhere