feat(sim): enable read noise by default and improve test infrastructure

- Set READ_NOISE_EN=1 as default in cam_top.sv
- Wire READ_NOISE_* parameters to NOISE_* makefile variables in cocotb-common.mk
- Add PYTHON env variable support in Makefile for test invocation
- Update .gitignore with glob patterns (**/sim_build/, **/results.xml, *.fst)
- Add justfile recipe for remote cam-test-top execution

hw/sim/Makefile

@@ -1,3 +1,4 @@
+PYTHON ?= python
 MODULE_TESTS := cam_core_banked match_engine_pipeline cam_write_noise cam_read_noise
 
 .PHONY: help test-all test-top test-modules test-module test-model test-perf clean $(MODULE_TESTS:%=test-module-%)
@@ -27,7 +28,7 @@ $(MODULE_TESTS:%=test-module-%):
 	$(MAKE) -C tests/modules/$(@:test-module-%=%)
 
 test-model:
-	uv run pytest tests/model -q
+	env -u PYTHONPATH -u PYTHONHOME $(PYTHON) -m pytest tests/model -q
 
 test-perf:
 	$(MAKE) -C tests/perf

hw/sim/mk/cocotb-common.mk

@@ -37,10 +37,10 @@ WRITE_NOISE_EN          ?= $(NOISE_EN)
 WRITE_NOISE_RATE_NUM    ?= $(NOISE_RATE_NUM)
 WRITE_NOISE_RATE_DEN    ?= $(NOISE_RATE_DEN)
 WRITE_NOISE_BITS        ?= $(NOISE_BITS)
-READ_NOISE_EN           ?=
-READ_NOISE_RATE_NUM     ?=
-READ_NOISE_RATE_DEN     ?=
-READ_NOISE_BITS         ?=
+READ_NOISE_EN           ?= $(NOISE_EN)
+READ_NOISE_RATE_NUM     ?= $(NOISE_RATE_NUM)
+READ_NOISE_RATE_DEN     ?= $(NOISE_RATE_DEN)
+READ_NOISE_BITS         ?= $(NOISE_BITS)
 
 ifneq ($(strip $(WRITE_NOISE_EN)),)
 COMPILE_ARGS += -GWRITE_NOISE_EN=$(WRITE_NOISE_EN)