fix(search): broaden whitespace collapse to all Unicode whitespace

Change collapse_whitespace() from is_ascii_whitespace() to is_whitespace()
so non-breaking spaces, em-spaces, and other Unicode whitespace characters
in search snippets are also collapsed into single spaces. Additionally
fix serde_json::to_value() call site to handle serialization errors
gracefully instead of unwrapping.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/cli/commands/search.rs

@@ -345,7 +345,7 @@ fn collapse_newlines(s: &str) -> String {
     let mut result = String::with_capacity(s.len());
     let mut prev_was_space = false;
     for c in s.chars() {
-        if c.is_ascii_whitespace() {
+        if c.is_whitespace() {
             if !prev_was_space {
                 result.push(' ');
                 prev_was_space = true;
@@ -606,7 +606,13 @@ pub fn print_search_results_json(
         data: response,
         meta: SearchMeta { elapsed_ms },
     };
-    let mut value = serde_json::to_value(&output).unwrap();
+    let mut value = match serde_json::to_value(&output) {
+        Ok(v) => v,
+        Err(e) => {
+            eprintln!("Error serializing search response: {e}");
+            return;
+        }
+    };
     if let Some(f) = fields {
         let expanded = crate::cli::robot::expand_fields_preset(f, "search");
         crate::cli::robot::filter_fields(&mut value, "results", &expanded);