test(windows): run the Windows code under Wine; theme preview parity

Windows was previously only compile-checked. With Wine 11 (staging)
and mingw available, scripts/windows-wine-test.sh (`just
test-windows-wine`) builds expat/FreeType/fontconfig for mingw under
target/wine-deps and runs the test suites of ghostty-vt, unicode,
datastruct, input, os, config, terminal, crash, termio and cli under
Wine (~2,700 tests). New termio/tests/exec_windows.rs drives real
cmd.exe children over ConPTY through Termio (output, exit codes,
typing, 120 KiB writes, stop, start failure). Fixes found: Windows
paths from fs::canonicalize leaked the \\?\ prefix (new
ghostty_os::path::realpath strips it like Zig); ghostty-font compiles
hb-ft for bundled HarfBuzz on Windows; ~25 tests had Unix assumptions.
Wine limitations are ignored with reasons (ResizePseudoConsole stub,
no POSIX rename over existing files) - docs/rewrite/notes/windows-wine.md.

+list-themes preview parity (former KNOWN_DIFFERENCES rows 5-9): the
search box ports vaxis TextInput (word navigation and editing bindings,
grapheme-wise editing), ASCII-only case folding, light initial colors
until terminal reports arrive (no COLORFGBG), and load errors end the
preview with exit 1; PTY tests compare with /usr/bin/ghostty.

Test Plan:
- just test-windows-wine
- cargo test -p ghostty-cli --test list_themes_pty
- cargo test --workspace --no-fail-fast (3601 passed)

crates/ghostty-config/src/theme.rs

@@ -381,9 +381,14 @@ mod tests {
         );
         let mut d = DiagnosticList::default();
         assert!(open(&e("/tmp"), None, &mut d).is_none());
+        // Windows cannot open a directory as a file (AccessDenied).
         assert_eq!(
             d.items()[0].message,
-            "not reading theme from \"/tmp\": it is a directory"
+            if cfg!(windows) {
+                "failed to load theme from the path \"/tmp\": error.AccessDenied"
+            } else {
+                "not reading theme from \"/tmp\": it is a directory"
+            }
         );
     }
 
@@ -469,7 +474,11 @@ mod tests {
             let mut d = DiagnosticList::default();
             assert!(open(&e(name), Some(&EncodedOs::from_path(&dir)), &mut d).is_none());
             assert!(
-                d.items()[0].message.ends_with("it is a directory"),
+                d.items()[0].message.ends_with(if cfg!(windows) {
+                    "error.AccessDenied"
+                } else {
+                    "it is a directory"
+                }),
                 "{}",
                 d.items()[0].message
             );
@@ -484,7 +493,10 @@ mod tests {
         std::fs::write(dir.join("themes/mytheme-zzz"), "background = #000000\n").unwrap();
         let mut d = DiagnosticList::default();
         let t = open(&e("mytheme-zzz"), Some(&EncodedOs::from_path(&dir)), &mut d).unwrap();
-        assert!(t.path.ends_with_plain("themes/mytheme-zzz"));
+        assert!(
+            t.path
+                .ends_with_plain(&format!("themes{}mytheme-zzz", std::path::MAIN_SEPARATOR))
+        );
         assert!(d.is_empty());
         std::fs::remove_dir_all(&dir).unwrap();
     }
@@ -493,7 +505,13 @@ mod tests {
     fn theme_not_found_lists_tried_paths() {
         let mut d = DiagnosticList::default();
         assert!(open(&e("nope-zzz"), Some(&e("/nonexistent-res")), &mut d).is_none());
-        assert!(d.items().iter().any(|x| x.message
-            == "theme \"nope-zzz\" not found, tried path \"/nonexistent-res/themes/nope-zzz\""));
+        let tried = std::path::Path::new("/nonexistent-res")
+            .join("themes")
+            .join("nope-zzz");
+        let want = format!(
+            "theme \"nope-zzz\" not found, tried path \"{}\"",
+            tried.display()
+        );
+        assert!(d.items().iter().any(|x| x.message == want));
     }
 }