perf(search): 4-7x faster searchContent hot path

src/benchmark.zig

@@ -88,6 +88,12 @@ fn benchSearch(explorer: *Explorer, query: []const u8, n: usize, alloc: std.mem.
         for (r) |e| alloc.free(e.line_text);
         alloc.free(r);
     }
+    if (cio.posixGetenv("CODEDB_BENCH_BREAKDOWN") != null) {
+        const b = explorer.last_search_breakdown;
+        var buf: [512]u8 = undefined;
+        const msg = std.fmt.bufPrint(&buf, "  breakdown[{s}]: t0={d}ns t05={d}ns t1={d}ns t2={d}ns rerank={d}ns tier_reached={d} cands={d} results={d}\n", .{ query, b.tier0_ns, b.tier05_ns, b.tier1_ns, b.tier2_ns, b.rerank_ns, b.tier_reached, b.candidate_count, b.result_count }) catch "";
+        cio.File.stderr().writeAll(msg) catch {};
+    }
     return .{ .name = query, .kind = "search", .hits = hits, .avg_ns = total / n };
 }
 
@@ -274,7 +280,7 @@ pub fn main(init: std.process.Init.Minimal) !void {
     cio.setProcessArgs(init.args.vector);
     var gpa: std.heap.DebugAllocator(.{}) = .init;
     defer _ = gpa.deinit();
-    const alloc = gpa.allocator();
+    const alloc = if (cio.posixGetenv("CODEDB_BENCH_CALLOC") != null) std.heap.c_allocator else gpa.allocator();
 
     var threaded: std.Io.Threaded = .init(alloc, .{});
     defer threaded.deinit();