refactor: replace typeof with type guard

[Alfred-Skyblue]

No description provided.

[sxzz]

LGTM

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	87.1 kB (-14 B)	33.1 kB (-3 B)	29.9 kB (+4 B)
vue.global.prod.js	133 kB (-14 B)	50 kB (-7 B)	44.8 kB (-3 B)

Usages

Name	Size	Gzip	Brotli
createApp	48.4 kB	19 kB	17.4 kB
createSSRApp	51.6 kB	20.3 kB	18.5 kB
defineCustomElement	50.7 kB (-14 B)	19.8 kB (-5 B)	18.1 kB (-2 B)
overall	61.7 kB	23.9 kB	21.7 kB

[codspeed-hq]

CodSpeed Performance Report

Merging #8505 will improve performances by 73.61%

_{Comparing Alfred-Skyblue:chore-general (1545396) with main (9fa8241)}

Summary

⚡ 1 improvements
✅ 52 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	Alfred-Skyblue:chore-general	Change
⚡	write reactive obj, read 1000 computeds	68.6 ms	39.5 ms	+73.61%

[yyx990803]

Thanks for the PR - it took a long time for me to decide to close this because I was thinking about how to explain the reasoning.

For one - these type guard helpers mainly serve to reduce code size as they minify into a single letter function call compared to the inline typeof checks. However this is only meaningful in client-oriented code - this is why the places they are not used are mostly in compilers, dev-only code paths, or the compat build (where we are a bit more lenient about code size).

A few of these changes (in the compat build's runtime code) might actually make sense, but as a while I don't think this PR is worth it considering the downside of a more noisy git blame history.