refactor(cam): extract match engine into separate module and centralize parameters

- Split cam_core into pure memory (cam_core.sv) and match engine (match_engine.sv)
- Add cam_params.svh with centralized parameter definitions (NUM_ROWS, HASH_BITS, LANES, etc.)
- Update cam_top.sv to use shared parameters and compose match_engine
- Update Makefile to include new match_engine module and correct Verilator define syntax

hw/rtl/cam_params.svh

@@ -0,0 +1,54 @@
+//==============================================================================
+// CAM Parameter Definitions
+//==============================================================================
+// This file defines shared compile-time parameters for the Content-Addressable
+// Memory (CAM) subsystem.  All `define macros use `ifndef guards to allow
+// command-line override via +define+.
+//
+// Macros:
+//   NUM_ROWS    — Number of rows in the CAM array
+//   HASH_BITS   — Width of the hash value in bits
+//   LANES       — Number of parallel comparison lanes
+//   ROW_BITS    — Bits needed to index NUM_ROWS rows ($clog2(NUM_ROWS))
+//   SCORE_BITS  — Bits needed to represent HASH_BITS-bit scores ($clog2(HASH_BITS+1))
+//
+// The TIE_BREAK_SENTINEL localparam is a bitmask with all bits set to 1'b1,
+// used as the initial / tie-breaking value in the row-priority arbiter.
+//==============================================================================
+
+`ifndef CAM_PARAMS_SVH
+`define CAM_PARAMS_SVH
+
+// Number of CAM rows.
+`ifndef NUM_ROWS
+`define NUM_ROWS 512
+`endif
+
+// Width of the hash value stored per row.
+`ifndef HASH_BITS
+`define HASH_BITS 512
+`endif
+
+// Number of parallel comparison lanes.
+`ifndef LANES
+`define LANES 16
+`endif
+
+// Bits required to represent a row index.
+`ifndef ROW_BITS
+`define ROW_BITS $clog2(`NUM_ROWS)
+`endif
+
+// Bits required to represent a full-score count.
+`ifndef SCORE_BITS
+`define SCORE_BITS $clog2(`HASH_BITS + 1)
+`endif
+
+// Tie-break sentinel: all ones in the row-index width.
+// Used as the initial best-index value before any match is found.
+localparam logic [(`ROW_BITS)-1:0] TIE_BREAK_SENTINEL = {(`ROW_BITS){1'b1}};
+
+// Current fixed parameters require NUM_ROWS divisible by LANES.
+// Non-divisible tail-group valid-mask is not implemented in this round.
+
+`endif // CAM_PARAMS_SVH