refactor(hw/sim): extract common cocotb make infrastructure into shared mk/ directory

- Split monolithic hw/sim/Makefile into modular include files (mk/cocotb-common.mk, mk/rtl-sources.mk)
- Add per-module test Makefiles (cam_core_banked, cam_read_noise, cam_write_noise, match_engine_pipeline, perf, top)
- Add missing simulation tools (yosys, graphviz, xdot) to devenv.nix
- Fix path handling in sweep_noise.py and test modules to be HASH_BITS-aware

devenv.nix

@@ -4,20 +4,26 @@
   config,
   inputs,
   ...
-}: let
+}:
+let
   pkgs-nixgl =
     (import inputs.nixpkgs {
       system = pkgs.stdenv.hostPlatform.system;
       config.allowUnfree = true;
-      overlays = [inputs.nixgl.overlay];
-    }).nixgl.override {
-      nvidiaVersionFile = "/proc/driver/nvidia/version";
-      nvidiaVersion = "580.126.09";
-    };
-in {
+      overlays = [ inputs.nixgl.overlay ];
+    }).nixgl.override
+      {
+        nvidiaVersionFile = "/proc/driver/nvidia/version";
+        nvidiaVersion = "580.126.09";
+      };
+in
+{
   packages = with pkgs; [
-      nil
-      verilator
+    nil
+    verilator
+    yosys
+    graphviz
+    xdot
   ];
 
   enterShell = ''