feat(oxfmt): add debug span for reading files (#28204)

Reading a file happens outside the `oxfmt::format` span, so time spent in I/O did not show up with `OXC_LOG=debug`.

On a machine where an endpoint security agent scans every `open()`/`close()`, most of the wall time was spent there, but the log only showed formatting time.

```
DEBUG oxfmt::read{path=src/foo.tsx}: oxfmt::cli::service: close time.busy=92.6µs time.idle=2.38µs
```

🤖 Generated with [Claude Code](https://claude.com/claude-code)

apps/oxfmt/src/cli/service.rs

@@ -7,6 +7,7 @@ use std::{
 
 use cow_utils::CowUtils;
 use rayon::prelude::*;
+use tracing::debug_span;
 
 use oxc_diagnostics::{DiagnosticSender, DiagnosticService};
 
@@ -44,7 +45,9 @@ impl FormatService {
             let start_time = matches!(self.format_mode, OutputMode::Check).then(Instant::now);
 
             let path = Arc::clone(&plan.path);
-            let Ok(source_text) = utils::read_to_string(&path) else {
+            let Ok(source_text) = debug_span!("oxfmt::read", path = %path.display())
+                .in_scope(|| utils::read_to_string(&path))
+            else {
                 // This happens if binary file is attempted to be formatted
                 // e.g. `.ts` for MPEG-TS video file
                 let diagnostics = DiagnosticService::wrap_diagnostics(