fix: inspector font/formatting, FreeType-only backend on Apple

Resolves the parity items of docs/rewrite/notes/review-rv17-codex.md
(final-Z20.md):
- FreeType-only font backend is also available on Apple targets
  (discovery-free, embedded emoji fonts); ghostty_surface_quicklook_font
  returns null for every backend except plain CoreText like Zig.
- The +list-fonts test keys off the font crate's selected backend
  (HAS_DISCOVERY), correct under feature unification and on Apple.
- Inspector font: 32 px rasterized with FreeType (dear-imgui freetype)
  like Ghostty; a new `visual-parity.sh inspector` scenario shows 0.031%
  differing pixels (hover highlight) vs the original on Linux. Windows,
  Apple and wasm keep stb_truetype at 32 px (registered as a deliberate
  deviation).
- Inspector DCS/APC descriptions follow Zig 0.15.2's formatting
  (checked by running Zig), incl. the terminal.Parser.Action prefix.
- The ImGui demo window appears only in dev-profile builds, mirroring
  Zig's .Debug-only gate.

Test Plan:
- cargo test --workspace --no-fail-fast (3582 passed)
- just check-macos (both, also with --features font-backend-freetype)
- scripts/visual-parity.sh inspector

crates/ghostty-cli/src/list_fonts.rs

@@ -134,20 +134,28 @@ pub fn run(args: &[impl AsRef<[u8]>]) -> Result<u8, Error> {
 
 #[cfg(test)]
 mod tests {
+    /// Keyed off the font crate's actually selected backend, not this
+    /// crate's own feature flag: cargo feature unification can enable
+    /// `ghostty-font/font-backend-freetype` without the CLI forwarding
+    /// feature, and on Apple targets the default backend (CoreText) has
+    /// discovery.
+    ///
     /// Without a discovery mechanism (the `freetype` font backend, Zig
     /// `Discover == void`) `+list-fonts` prints the compile-time-option
     /// message and exits with 1, after parsing the arguments.
-    #[cfg(feature = "font-backend-freetype")]
     #[test]
-    fn freetype_backend_reports_no_discovery() {
-        const { assert!(!ghostty_font::HAS_DISCOVERY) };
-        assert_eq!(super::run(&[] as &[&[u8]]).expect("run"), 1);
-        assert!(super::NO_DISCOVERY_MESSAGE.ends_with("try again."));
-    }
-
-    #[cfg(not(feature = "font-backend-freetype"))]
-    #[test]
-    fn default_backend_has_discovery() {
-        const { assert!(ghostty_font::HAS_DISCOVERY) };
+    fn discovery_presence_follows_selected_backend() {
+        let backend = ghostty_font::options.backend;
+        assert_eq!(
+            ghostty_font::HAS_DISCOVERY,
+            backend.has_fontconfig() || backend.has_coretext()
+        );
+        if ghostty_font::HAS_DISCOVERY {
+            assert_ne!(backend, ghostty_font::Backend::Freetype);
+        } else {
+            assert_eq!(backend, ghostty_font::Backend::Freetype);
+            assert_eq!(super::run(&[] as &[&[u8]]).expect("run"), 1);
+            assert!(super::NO_DISCOVERY_MESSAGE.ends_with("try again."));
+        }
     }
 }