refactor(cam): rename read-noise path to read-pass-through and reorganize test module structure

- Rename `read_noise` scenarios and noise_mode to `read_pass_through` across
  run_cam_correctness.py, test_run_cam_correctness.py, and Makefiles
- Update RTL comment in match_engine_pipeline.sv to reflect pass-through behavior
- Move unit-level cocotb tests from `tests.test_*` flat namespace to
  `tests.modules.*` and `tests.top.*` subdirectory layout, matching actual
  Makefile paths (hw/sim/tests/modules/..., hw/sim/tests/top/...)
- Remove redundant dual-noise subtarget from read_noise/Makefile
- Update help text and docs to reflect read-path pass-through semantics
- Add .codegraph to .gitignore

scripts/run_cam_correctness.py

@@ -80,18 +80,18 @@ default_scenarios: list[Scenario] = [
         expected="bit_flip_injected",
     ),
     Scenario(
-        name="cam_top_read_noise",
+        name="cam_top_read_path",
         kind="cocotb",
         module="tests.top.read_noise.test_read_noise",
         testcase=None,
         params={},
-        noise_mode="read_noise",
-        expected="read_perturbed",
+        noise_mode="read_pass_through",
+        expected="pure_matching",
     ),
     Scenario(
         name="cam_core_banked",
         kind="cocotb",
-        module="tests.test_cam_core_banked",
+        module="tests.modules.cam_core_banked.test_cam_core_banked",
         testcase=None,
         params={},
         noise_mode="none",
@@ -100,7 +100,7 @@ default_scenarios: list[Scenario] = [
     Scenario(
         name="match_engine_pipeline",
         kind="cocotb",
-        module="tests.test_match_engine_pipeline",
+        module="tests.modules.match_engine_pipeline.test_match_engine_pipeline",
         testcase=None,
         params={},
         noise_mode="none",
@@ -109,20 +109,20 @@ default_scenarios: list[Scenario] = [
     Scenario(
         name="cam_write_noise",
         kind="cocotb",
-        module="tests.test_cam_write_noise",
+        module="tests.modules.cam_write_noise.test_cam_write_noise",
         testcase=None,
         params={},
         noise_mode="write_noise",
         expected="bit_flip_injected",
     ),
     Scenario(
-        name="cam_read_noise",
+        name="cam_read_path",
         kind="cocotb",
-        module="tests.test_cam_read_noise",
+        module="tests.modules.cam_read_noise.test_cam_read_noise",
         testcase=None,
         params={},
-        noise_mode="read_noise",
-        expected="read_perturbed",
+        noise_mode="read_pass_through",
+        expected="pass_through",
     ),
     Scenario(
         name="ref_model_noise",
@@ -145,11 +145,11 @@ default_scenarios: list[Scenario] = [
 _MAKE_DIR: dict[str, str] = {
     "cam_top_basic": "top/no_noise",
     "cam_top_write_noise": "top/write_noise",
-    "cam_top_read_noise": "top/read_noise",
+    "cam_top_read_path": "top/read_noise",
     "cam_core_banked": "modules/cam_core_banked",
     "match_engine_pipeline": "modules/match_engine_pipeline",
     "cam_write_noise": "modules/cam_write_noise",
-    "cam_read_noise": "modules/cam_read_noise",
+    "cam_read_path": "modules/cam_read_noise",
 }
 
 
@@ -493,8 +493,8 @@ def write_summary_md(
     lines.append("")
     lines.append(
         "- **cam_top**: 通过 `cam_top_basic`、`cam_top_write_noise`、"
-        "`cam_top_read_noise` 三个场景覆盖顶层 CAM 模块的基本功能、"
-        "写入噪声注入和读取噪声注入路径"
+        "`cam_top_read_path` 三个场景覆盖顶层 CAM 模块的基本功能、"
+        "写入噪声注入和读取路径 pass-through"
     )
     lines.append(
         "- **cam_core_banked**: 通过 `cam_core_banked` 场景覆盖"
@@ -513,8 +513,8 @@ def write_summary_md(
         "写入噪声注入路径"
     )
     lines.append(
-        "- **cam_read_noise**: 通过 `cam_read_noise` 场景独立覆盖"
-        "读取噪声注入路径"
+        "- **cam_read_noise**: 通过 `cam_read_path` 场景独立覆盖"
+        "读取路径 pass-through"
     )
     lines.append("")
     lines.append("## 论文可引用结论草稿")