feat(rag): add claw-rag-service

Adds claw-rag-service for repository indexing and semantic search.

rust/crates/claw-rag-service/src/chunk.rs

@@ -0,0 +1,41 @@
+//! Split file text into overlapping windows (character-based UTF-8).
+
+#[must_use]
+pub fn chunk_text(text: &str, max_chars: usize, overlap: usize) -> Vec<String> {
+    if max_chars == 0 {
+        return Vec::new();
+    }
+    let overlap = overlap.min(max_chars.saturating_sub(1));
+    let mut out = Vec::new();
+    let chars: Vec<char> = text.chars().collect();
+    if chars.is_empty() {
+        return out;
+    }
+    let mut start = 0;
+    loop {
+        let end = (start + max_chars).min(chars.len());
+        let piece: String = chars[start..end].iter().collect();
+        if !piece.trim().is_empty() {
+            out.push(piece);
+        }
+        if end >= chars.len() {
+            break;
+        }
+        let step = max_chars.saturating_sub(overlap).max(1);
+        start += step;
+    }
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn chunks_non_empty() {
+        let c = chunk_text("hello world test", 5, 2);
+        assert!(!c.is_empty());
+        let joined: String = c.join("");
+        assert!(joined.contains("hello"));
+    }
+}