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-core/src/surface/mod.rs

@@ -745,6 +745,10 @@ impl Surface {
     #[cfg(target_vendor = "apple")]
     #[must_use]
     pub fn quicklook_font(&self, scale: f32) -> Option<*mut std::ffi::c_void> {
+        // For non-CoreText (and the other CoreText variants) we return none.
+        if ghostty_font::options.backend != ghostty_font::Backend::Coretext {
+            return None;
+        }
         let grid = self.renderer.font_grid();
         let mut state = grid.write();
         let face = state
@@ -752,12 +756,7 @@ impl Surface {
             .collection
             .get_face(ghostty_font::collection::Index::default())
             .ok()?;
-        let font = face.quicklook_font(f64::from(scale));
-        Some(
-            objc2_core_foundation::CFRetained::into_raw(font)
-                .as_ptr()
-                .cast(),
-        )
+        ghostty_font::face::quicklook_font_raw(face, f64::from(scale))
     }
 
     /// Current sizes.