feat(rag): add claw-rag-service

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

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

@@ -0,0 +1,87 @@
+//! Vector search over indexed chunks (linear scan MVP).
+
+use std::path::Path;
+
+use reqwest::Client;
+
+use crate::db::{load_all_indexed, open_db};
+use crate::embed::{cosine_similarity, embed_batch, EmbedConfig};
+use crate::{QueryRequest, QueryResponse, RagHit};
+
+pub async fn query_index(
+    db_path: &Path,
+    client: &Client,
+    cfg: &EmbedConfig,
+    req: &QueryRequest,
+) -> Result<QueryResponse, String> {
+    if !db_path.is_file() {
+        return Ok(QueryResponse {
+            hits: Vec::new(),
+            phase: "1-sqlite-no-db",
+        });
+    }
+
+    let conn = open_db(db_path)?;
+    let qvecs = embed_batch(client, cfg, std::slice::from_ref(&req.query)).await?;
+    let q = qvecs
+        .into_iter()
+        .next()
+        .ok_or_else(|| "no query embedding".to_string())?;
+
+    #[cfg(feature = "qdrant-index")]
+    if let Ok(Some(r)) = crate::qdrant_index::query_qdrant(&q, req.top_k).await {
+        return Ok(r);
+    }
+
+    let rows = load_all_indexed(&conn)?;
+    drop(conn);
+
+    if rows.is_empty() {
+        return Ok(QueryResponse {
+            hits: Vec::new(),
+            phase: "1-sqlite-empty",
+        });
+    }
+
+    let expected = rows[0].vec.len();
+    if q.len() != expected {
+        return Err(format!(
+            "embedding dimension mismatch: index uses dim {} but query embedding has {} (same model/env as ingest required)",
+            expected, q.len()
+        ));
+    }
+
+    let mut scored: Vec<(f32, usize)> = rows
+        .iter()
+        .enumerate()
+        .map(|(i, r)| (cosine_similarity(&q, &r.vec), i))
+        .collect();
+    scored.sort_by(|a, b| b.0.partial_cmp(&a.0).unwrap_or(std::cmp::Ordering::Equal));
+
+    let top = req.top_k.min(64) as usize;
+    let hits: Vec<RagHit> = scored
+        .into_iter()
+        .take(top)
+        .map(|(score, i)| {
+            let r = &rows[i];
+            RagHit {
+                path: r.path.clone(),
+                snippet: truncate_snippet(&r.text, 480),
+                score: Some(score),
+            }
+        })
+        .collect();
+
+    Ok(QueryResponse {
+        hits,
+        phase: "1-sqlite",
+    })
+}
+
+fn truncate_snippet(s: &str, max_chars: usize) -> String {
+    let n = s.chars().count();
+    if n <= max_chars {
+        return s.to_string();
+    }
+    s.chars().take(max_chars).collect::<String>() + "…"
+}