fix: harden LLM providers, UTF-8 handling, and webhook/batch reliability

- webclaw-llm: add explicit request + connect timeouts to the reqwest
  client in every provider (anthropic, openai, ollama) with a shorter
  timeout on the ollama health check, so a stalled provider fails fast.
- webclaw-llm: fix a panic when truncating a provider error body that
  contains multibyte characters near the 500-char cut (char-safe take).
- webclaw-core: snap the endpoint-scan budget cut to a UTF-8 char
  boundary so oversized scripts with non-ASCII content no longer panic.
- webclaw-core: rewrite js_literal_to_json to copy raw bytes instead of
  `byte as char`, preserving multibyte UTF-8 in SvelteKit string values
  rather than producing Latin-1 mojibake.
- webclaw-cli: have fire_webhook return its JoinHandle and await it at
  the crawl/batch/batch-llm call sites, removing the fixed 500ms sleeps.
- webclaw-mcp: drop the up-front DNS pre-validation loop in batch that
  aborted the whole request on one bad URL; the fetch layer already
  applies the same SSRF guard per URL and reports per-URL errors.
- webclaw-fetch: include the port in the warmup homepage URL so hosts
  on a non-default port are warmed correctly.

Adds regression tests for the UTF-8 endpoint-scan and SvelteKit cases.

crates/webclaw-fetch/src/client.rs

@@ -801,11 +801,17 @@ fn is_challenge_html(html: &str) -> bool {
     false
 }
 
-/// Extract the homepage URL (scheme + host) from a full URL.
+/// Extract the homepage URL (scheme + host[:port]) from a full URL.
 fn extract_homepage(url: &str) -> Option<String> {
-    url::Url::parse(url)
-        .ok()
-        .map(|u| format!("{}://{}/", u.scheme(), u.host_str().unwrap_or("")))
+    url::Url::parse(url).ok().map(|u| {
+        let host = u.host_str().unwrap_or("");
+        // `port()` is `Some` only for a non-default port; include it so a
+        // host like example.com:8443 is warmed on the right port.
+        match u.port() {
+            Some(port) => format!("{}://{}:{}/", u.scheme(), host, port),
+            None => format!("{}://{}/", u.scheme(), host),
+        }
+    })
 }
 
 /// Convert a webclaw-pdf PdfResult into a webclaw-core ExtractionResult.