fix: Windows core build, embedded init, byte-exact paths, version info

Closes the remaining core/lib/termio/GTK rows (final-Z2.md):
- ghostty-core compiles for Windows (Unix-only exec fields and file
  modes gated); checked with cargo check --target x86_64-pc-windows-gnu.
- Embedded init: ensure_locale, SIGPIPE ignored in ghostty_init for
  C/Swift hosts, Apple crash tags; the argv passed to ghostty_init feeds
  ghostty_config_load_cli_args; ghostty_config_load_file accepts
  non-UTF-8 paths.
- OSC 7 pwd, embedded surface cwd/command/env/initial input,
  ghostty_surface_text and GTK file drops keep raw bytes.
- XTVERSION, TERM_PROGRAM_VERSION, the About dialog and crash metadata
  use ghostty_build_info instead of hardcoded versions.

Test Plan:
- cargo test --workspace (3327 passed)
- cargo clippy --workspace --all-targets -- -D warnings

crates/ghostty-termio/src/exec.rs

@@ -181,7 +181,7 @@ impl Exec {
         // set that on the terminal now. This allows rapidly initializing
         // new surfaces to use the proper pwd.
         if let Some(cwd) = &self.subprocess.cwd
-            && let Err(err) = term.set_pwd(cwd.as_bytes())
+            && let Err(err) = term.set_pwd(&ghostty_os::osbytes::config_str_to_bytes(cwd))
         {
             log::warn!("error setting initial pwd err={err:?}");
         }
@@ -907,7 +907,10 @@ impl Subprocess {
 
         // Add the environment variables that override any others.
         for (k, v) in cfg.env_override.iter() {
-            env.insert(k, v);
+            env.insert(
+                ghostty_os::osbytes::config_str_to_os(k),
+                ghostty_os::osbytes::config_str_to_os(v),
+            );
         }
 
         // Build our args list
@@ -925,7 +928,7 @@ impl Subprocess {
         // https://github.com/kovidgoyal/kitty/issues/1595
         // https://github.com/ghostty-org/ghostty/discussions/7769
         if let Some(pwd) = &cwd {
-            env.insert("PWD", pwd.clone());
+            env.insert("PWD", ghostty_os::osbytes::config_str_to_os(pwd));
         }
 
         Ok(Subprocess {
@@ -1037,7 +1040,7 @@ impl Subprocess {
                 }
             }
             Some(proposed) => {
-                if std::path::Path::new(proposed).exists() {
+                if std::path::Path::new(&ghostty_os::osbytes::config_str_to_os(proposed)).exists() {
                     Some(proposed.clone())
                 } else {
                     log::warn!("cannot access cwd, ignoring: {proposed}");