perf: index filename candidates and avoid full-corpus retrieval scans

crates/searchi-core/benchmarks/results/windows-cpu-small.json

@@ -0,0 +1,45 @@
+{
+  "fixture": "synthetic SQLite metadata and text; no filesystem extraction or semantic inference",
+  "files": 10000,
+  "documents": 1000,
+  "seed_seconds": 0.3428201,
+  "database_bytes": 3207168,
+  "database_path": "target/benchmarks/small.db",
+  "architecture": "x86_64",
+  "os": "windows",
+  "cpu_only": true,
+  "queries": [
+    {
+      "query": "invoice_0009999.txt",
+      "samples": 20,
+      "p50_ms": 3.0624,
+      "p95_ms": 3.8085,
+      "target_p95_ms": 50.0,
+      "target_met": true
+    },
+    {
+      "query": "invoice_",
+      "samples": 20,
+      "p50_ms": 20.8847,
+      "p95_ms": 28.4805,
+      "target_p95_ms": 50.0,
+      "target_met": true
+    },
+    {
+      "query": "marker0000999",
+      "samples": 20,
+      "p50_ms": 1.7667,
+      "p95_ms": 2.7321,
+      "target_p95_ms": 150.0,
+      "target_met": true
+    },
+    {
+      "query": "cancellation",
+      "samples": 20,
+      "p50_ms": 12.2173,
+      "p95_ms": 16.5439,
+      "target_p95_ms": 150.0,
+      "target_met": true
+    }
+  ]
+}