Add diagnostic logging to debug CI segfault

Add step-by-step debug logging in spawn_blocking to identify exactly
where the crash occurs:
- After spawn_blocking starts
- After ThreadScope::new()
- After sapi.startup()
- After RequestContext::new()
- After RequestContext::set_current()
- Before and after first estrdup call

Also reverts the incorrect change that removed php_module_startup calls
from Sapi::startup() - per-thread initialization IS supposed to call
php_module_startup.

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

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: Qard

src/embed.rs

@@ -341,14 +341,17 @@ impl Handler for Embed {
 
     // Spawn blocking PHP execution - ALL PHP operations happen here
     let blocking_handle = tokio::task::spawn_blocking(move || {
+      eprintln!("[DEBUG 1] spawn_blocking started");
       // Initialize thread-local storage for this worker thread
       let _thread_scope = ThreadScope::new();
+      eprintln!("[DEBUG 2] ThreadScope::new() completed");
       // Call SAPI startup on THIS thread to initialize PHP's memory allocator.
       // This is required before any estrdup calls can be made.
       // The startup call is serialized via write lock to prevent concurrent php_module_startup.
       _sapi
         .startup()
         .map_err(|_| EmbedRequestError::SapiNotStarted)?;
+      eprintln!("[DEBUG 3] sapi.startup() completed");
 
       // Setup RequestContext (always streaming from SAPI perspective)
       // RequestContext::new() will extract the request body's read stream and add it as RequestStream extension
@@ -358,19 +361,16 @@ impl Handler for Embed {
         response_writer.clone(),
         headers_sent_tx,
       );
+      eprintln!("[DEBUG 4] RequestContext::new() completed");
       RequestContext::set_current(Box::new(ctx));
+      eprintln!("[DEBUG 5] RequestContext::set_current() completed");
 
       // All estrdup calls happen here, inside spawn_blocking, after ThreadScope::new()
       // has initialized PHP's thread-local storage. These will be freed by efree in
       // sapi_module_deactivate during request shutdown.
-      // DEBUG: Log values before estrdup to identify invalid inputs
-      eprintln!("[DEBUG] request_uri_str: {:?}", request_uri_str);
-      eprintln!("[DEBUG] translated_path_str: {:?}", translated_path_str);
-      eprintln!("[DEBUG] method_str: {:?}", method_str);
-      eprintln!("[DEBUG] query_str: {:?}", query_str);
-      eprintln!("[DEBUG] content_type_str: {:?}", content_type_str);
-
+      eprintln!("[DEBUG 6] About to call estrdup for request_uri_str: {:?}", request_uri_str);
       let request_uri_c = estrdup(request_uri_str.as_str());
+      eprintln!("[DEBUG 7] estrdup(request_uri_str) completed");
       let path_translated = estrdup(translated_path_str.as_str());
       let request_method = estrdup(method_str.as_str());
       let query_string = estrdup(query_str.as_str());