fix(asset-canister): fix skill errors, add npm versions and evals

[marc0olo]

Summary

Fixes factual errors in the asset-canister skill, wraps top-level await in code examples, adds npm versions, and creates the first evaluation suite.

Mentions #97, #95, #96, #100.

Changes

Skill (asset-canister/SKILL.md):

• Wrap all await in async function manageAssets() (no top-level await)
• Fix import for fs — was mid-block (invalid ES module syntax), moved to top
• Add npm versions to prerequisites (@icp-sdk/canisters >= 3.5.0, @icp-sdk/core >= 5.0.0)
• Replace all source references with dir (dfx terminology → icp-cli)
• Fix pitfall #1: source → configuration.dir
• Fix pitfall #3: clarify configuration.build is optional, dir must have content
• Add pitfall #7: asset canister Wasm version must be >= 0.30.2 for ic_env cookie support
• Add note in programmatic uploads: shouldFetchRootKey is for Node.js scripts only, browser frontends should use rootKey from ic_env cookie
• Fix custom domain registration: replace "registration is automatic" with the actual validate + POST flow (https://icp0.io/custom-domains/v1/<domain>/validate and POST .../v1/<domain>)
• Remove unrelated Motoko backend canister from icp.yaml example

Evaluations (evaluations/asset-canister.json): New file with 4 output evals + 12 trigger evals

• Programmatic asset upload (Node.js context)
• SPA routing configuration (.ic-assets.json5)
• Asset canister recipe setup (icp.yaml)
• Security: shouldFetchRootKey in Node.js scripts