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)

justfile

@@ -282,6 +282,11 @@ check-macos target="aarch64-apple-darwin":
 check-windows:
     scripts/windows-crosscheck.sh
 
+# Run the Windows test suites under Wine (builds expat/FreeType/fontconfig for
+# mingw on the first run; see docs/rewrite/notes/windows-wine.md).
+test-windows-wine *args:
+    scripts/windows-wine-test.sh {{ args }}
+
 # Build, lint and test the wasm32 targets.
 check-wasm:
     scripts/wasm-check.sh