fix: C action buffer lengths, byte-faithful callbacks, runtime finalize

Resolves the 8 gaps in docs/rewrite/notes/review-rv10-codex.md
(final-Z13.md):
- P1 memory safety: the C key-table action (and hovered-link/open-URL
  payloads) could advertise a length larger than the NUL-truncated
  allocation. A counted_bytes helper now passes the full bytes plus a
  trailing NUL with len == byte count, like Zig's backing slices; all
  C pointer+len structs were audited and tested to read exactly len.
- ghostty-bench args follow cli/args.zig (ordered duplicates, empty
  value resets, first bad value errors, parseBool spellings); the C
  benchmark tokenizer uses the ArgIteratorGeneral port.
- OSC 7 derived titles, desktop notifications and OSC 8 hover links
  forward raw bytes to the runtime; GTK converts only for display.
- C diagnostic getter exports original bytes; escaped surrogates report
  Utf8CannotEncodeSurrogateHalf; config float formatters print `nan`.
- Config::finalize_for(AppRuntime): GTK-only finalization (gtk-single-
  instance=detect) and termio's cgroup hooks apply only to the GTK
  runtime, so libghostty keeps `detect` like Zig.

Test Plan:
- cargo test --workspace --no-fail-fast (exit 0)
- cargo test -p ghostty-lib --features test-platform
- just check-wasm (macOS/Windows clippy re-run after the concurrent
  terminal changes land)

crates/ghostty-core/src/surface/clipboard.rs

@@ -358,7 +358,7 @@ impl Surface {
 
     /// Show a desktop notification, rate limited (Zig
     /// `showDesktopNotification`).
-    pub(crate) fn show_desktop_notification(&self, title: &str, body: &str) {
+    pub(crate) fn show_desktop_notification(&self, title: &[u8], body: &[u8]) {
         let now = Instant::now();
 
         // Set a limit of one desktop notification per second so that the OS
@@ -391,8 +391,8 @@ impl Surface {
         self.app.last_notification_time.set(Some(now));
         self.app.last_notification_digest.set(new_digest);
         self.perform(RtAction::DesktopNotification(DesktopNotification {
-            title: title.to_owned(),
-            body: body.to_owned(),
+            title: ghostty_os::osbytes::EncodedOs::from_bytes(title),
+            body: ghostty_os::osbytes::EncodedOs::from_bytes(body),
         }));
     }
 

crates/ghostty-core/src/surface/keyboard.rs

@@ -514,7 +514,9 @@ impl Surface {
             // we reset state
             self.perform(RtAction::MouseShape(mouse_shape));
             self.perform(RtAction::MouseOverLink(
-                ghostty_apprt::action::MouseOverLink { url: String::new() },
+                ghostty_apprt::action::MouseOverLink {
+                    url: ghostty_os::osbytes::EncodedOs::new(),
+                },
             ));
             self.queue_render();
         }

crates/ghostty-core/src/surface/mod.rs

@@ -960,9 +960,7 @@ impl Surface {
                     return Ok(());
                 }
 
-                let title = String::from_utf8_lossy(notification.title()).into_owned();
-                let body = String::from_utf8_lossy(notification.body()).into_owned();
-                self.show_desktop_notification(&title, &body);
+                self.show_desktop_notification(notification.title(), notification.body());
             }
 
             Message::RendererHealth(health) => self.update_renderer_health(health),

crates/ghostty-core/src/surface/mouse.rs

@@ -1801,7 +1801,9 @@ impl Surface {
                         trim: false,
                     });
                     (
-                        Some(MouseOverLink { url: str }),
+                        Some(MouseOverLink {
+                            url: ghostty_os::osbytes::EncodedOs::from_plain_text(&str),
+                        }),
                         cfg.link_previews == LinkPreviews::True,
                     )
                 }
@@ -1814,9 +1816,8 @@ impl Surface {
                         break 'link (None, false);
                     };
                     (
-                        // Display-only text for the status bar.
                         Some(MouseOverLink {
-                            url: String::from_utf8_lossy(&uri).into_owned(),
+                            url: ghostty_os::osbytes::EncodedOs::from_bytes(&uri),
                         }),
                         cfg.link_previews != LinkPreviews::False,
                     )
@@ -1848,7 +1849,7 @@ impl Surface {
             out.actions
                 .push(RtAction::MouseShape(st.terminal.mouse_shape));
             out.actions.push(RtAction::MouseOverLink(MouseOverLink {
-                url: String::new(),
+                url: ghostty_os::osbytes::EncodedOs::new(),
             }));
             out.render = true;
         }
@@ -1930,7 +1931,7 @@ impl Surface {
                 let shape = self.lock_terminal().mouse_shape;
                 self.perform(RtAction::MouseShape(shape));
                 self.perform(RtAction::MouseOverLink(MouseOverLink {
-                    url: String::new(),
+                    url: ghostty_os::osbytes::EncodedOs::new(),
                 }));
                 self.queue_render();
             }