feat(crash): Breakpad-style minidumps on macOS and Windows

Ghostty links sentry-native with the breakpad backend on every platform
(SharedDeps.zig), so it writes minidumps on macOS and Windows as well.
- macOS: a Mach exception port handler thread (structured like
  Breakpad's exception_handler) catches EXC_BAD_ACCESS/BAD_INSTRUCTION/
  ARITHMETIC/BREAKPOINT, suspends other threads, reads the crashed
  thread state and writes a minidump via minidump-writer as the
  event.minidump attachment, then restores the previous ports so the
  BSD signal and default termination follow. The signal path remains
  the fallback (and handles SIGABRT); a watchdog alarm bounds dumping.
- Windows: SetUnhandledExceptionFilter hands off to a pre-started dump
  thread using minidump-writer's dump_crash_context.
- The screen-file open action decodes the escaped path to raw OS bytes
  (also for the C action passed to embedders).

macOS/Windows code is compile-checked (clippy -D warnings) only; the
shared Mach message decoding and minidump attachment logic have Linux
unit tests. Platform matrix in docs/rewrite/notes/crash-CR.md.

Test Plan:
- cargo test --workspace (3348 passed)
- just check-macos; just check-macos x86_64-apple-darwin; just check-windows

crates/ghostty-lib/src/action_c.rs

@@ -183,8 +183,11 @@ pub fn action_to_c(action: &Action, keep: &mut Keep) -> ghostty_action_s {
         }
         Action::OpenUrl(u) => {
             v.open_url.kind = u.kind as c_int;
-            v.open_url.url = keep.cstr(&u.url);
-            v.open_url.len = u.url.len();
+            // The URL may be the escaped form of a non-UTF-8 path; hand the
+            // embedder the real bytes.
+            let url = ghostty_os::osbytes::config_str_to_bytes(&u.url);
+            v.open_url.url = keep.cstr_bytes(&url);
+            v.open_url.len = url.len();
         }
         Action::ShowChildExited(c) => {
             v.child_exited.exit_code = c.exit_code;