Misc: setup, fish, auto, helix, starship, system

- Setup: add Fedora guides, Signal, Dynamic Desktop, and Flatseal
- Shells: fix $() on older fish versions and unalias batcat on Fedora
- Auto:
    - Detect git dependency
    - Add .clang-format for C/C++ family
    - Add full-setup script
- Helix: update to 24.03, add text width, rulers, and fix reflow
- Rust: fix fish env
- Starship: fix config path
- System: rename mac fnmode scripts and update sshd_config

manual/rust/rust-configure

@@ -14,7 +14,7 @@ use std::{
 
 const ENV: &str = r#". "$HOME/.cargo/env""#;
 // until the release of https://github.com/rust-lang/rustup/pull/3506/files
-const ENV_FISH: &str = r#"export PATH="$HOME/.cargo/bin:$PATH""#;
+const ENV_FISH: &str = r#"set -x PATH "$HOME/.cargo/bin" $PATH"#;
 
 fn main() -> anyhow::Result<()> {
 	let home = dirs::home_dir().context("can't find home directory")?;