Installer: make ' + c type ç for Portuguese speakers on a US keyboard

[pedroolivy]

The problem

People who type Portuguese on a US physical keyboard, which is very common among developers in Brazil and Portugal, can't get ç out of the box. With us + intl, ' + c gives ć. The compose table follows the system locale, and most of us keep the system in English (en_US), whose table maps <dead_acute> <c> to ć. The pt_BR and pt_PT tables already map it to ç.

Today everyone fixes this by hand. #2979 collected the same workaround from many people between Oct 2025 and Jul 2026, and #7601 documents it.

The idea

Building on #8117 (US International in the installer):

1. The user picks English (US, International).
2. The installer already guesses the timezone with tzupdate. If it points to Brazil or Portugal, it asks one question, defaulting to yes: "Do you type Portuguese? This makes ' + c type ç."
3. On yes, it makes ' + c type ç while keeping English menus, either by generating pt_BR.UTF-8 (or pt_PT.UTF-8) and setting only LC_CTYPE to it, as suggested in Document the ç override on the US International layout #7601, or by adding the two-line override from Document the ç override on the US International layout #7601 to ~/.XCompose.

Why this is safe

• Nothing changes unless someone picked US International and said they type Portuguese. Polish, Croatian and Serbian users keep ć.
• It reuses what Omarchy already has: the timezone guess and the per-locale compose tables.
• It matches Windows, where US International already types ç for ' + c.

Why ask instead of detecting silently

A timezone is only a guess: a Brazilian living abroad, or someone in Brazil who doesn't type Portuguese. One question with a sensible default covers both.

Happy to send a PR once #8117 lands, if this direction works for you.