Fix typo: instal → install in README

[Jah-yee]

Good first issue. In README.md, the ClawHub install command has a typo: clawhub instal linear should be clawhub install linear. One-word fix.

[a6091731]

Quick validation from current main: README now shows clawhub install linear (already corrected).

If this issue is still intended to track another location with the same typo, I can submit a follow-up patch for that file too.