refactor(cli): improve error handling for local script reading

[mostuselessboy]

Suggests an improvement

This PR standardizes error handling while reading a local scripts, bringing all of it in line with the recent improvements made to remote script fetching made in this commit (#1408).

Usage demo

import {$} from 'zx'

// Before: RAW Node.js ENOENT stack trace
// After: Clean user error
await $`npx zx non-existent.mjs`
// stderr: Error: Can't read non-existent.mjs
//         Failed to read local script: non-existent.mjs (ENOENT...)

• Build: I’ve run npm run build before committing and verified the bundle updates correctly.
• Tests: I’ve run test (node --test test/cli.test.js) and confirmed the new assertions pass.
• Docs: N/A (Internal error handling improvement).
• Sign Commits have verified signatures and follow conventional commits spec
• CoC: My changes follow the project’s coding guidelines and Code of Conduct.
• Review: This PR represents original work and is not solely generated by AI tools.

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[antongolub]

1. Pull this into a separate function readScriptFromFile
2. rm console.error. The exception will be caught and logged via main try-catch.
3. Rollback scripts/*.mjs edits. Keep the PR purpose focus.