chore(ledger): n22 合入后回填台账/凭证/覆盖率基线

task/n22-flush 合入（merge 6f99dea）：vol_idle_sync 空闲 flush 兜底。
Code 215,744→215,932（+188 B）、RW 1,224→1,232（+8 B）、ZI 不变；
RW_IRAM1 75,792 B（57.8%）、CCM 57,376 B（87.9%）不变——lane-f 分支侧
--no-verify 欠账清。覆盖率基线登记 vol_idle_sync.c（36/36 套件）。
凭证重盖（L0c 恢复序列）。

scripts/test_coverage_baseline.json

@@ -88,6 +88,14 @@
       "lines_covered": 27,
       "lines_valid": 29
     },
+    "App/fs/vol_idle_sync.c": {
+      "func_rate": 1.0,
+      "funcs_covered": 1,
+      "funcs_valid": 1,
+      "line_rate": 1.0,
+      "lines_covered": 21,
+      "lines_valid": 21
+    },
     "App/fs/vol_lock.c": {
       "func_rate": 1.0,
       "funcs_covered": 3,
@@ -564,6 +572,13 @@
       "lines_total": 99,
       "ok": true
     },
+    "vol_idle_sync": {
+      "files": {
+        "App/fs/vol_idle_sync.c": 21
+      },
+      "lines_total": 21,
+      "ok": true
+    },
     "vol_lock": {
       "files": {
         "App/fs/vol_lock.c": 17
@@ -593,6 +608,7 @@
     "App/cfg/cfg_file.c",
     "App/cfg/cfg_file_store_mcu.c",
     "App/cfg/prot_set_store.c",
+    "App/fs/vol_idle_sync.c",
     "App/fs/vol_lock.c",
     "App/log/console_log.c",
     "App/log/soe_rec.c",
@@ -623,16 +639,16 @@
   ],
   "totals": {
     "files_generated_excluded": 5,
-    "files_tested": 38,
-    "files_untested": 115,
-    "func_rate": 0.9258,
-    "funcs_covered": 412,
-    "funcs_valid": 445,
-    "line_rate": 0.8965,
-    "lines_covered": 5802,
-    "lines_valid": 6472,
-    "modules_ok": 35,
-    "modules_total": 35
+    "files_tested": 39,
+    "files_untested": 116,
+    "func_rate": 0.926,
+    "funcs_covered": 413,
+    "funcs_valid": 446,
+    "line_rate": 0.8968,
+    "lines_covered": 5823,
+    "lines_valid": 6493,
+    "modules_ok": 36,
+    "modules_total": 36
   },
   "untested_sources": [
     {
@@ -656,7 +672,7 @@
       "path": "Drivers/BSP/UI/ui_content_page.c"
     },
     {
-      "code_lines": 281,
+      "code_lines": 282,
       "path": "App/task/default_task.c"
     },
     {
@@ -1039,6 +1055,10 @@
       "code_lines": 11,
       "path": "Drivers/BSP/dbg_cfg.h"
     },
+    {
+      "code_lines": 10,
+      "path": "App/fs/vol_idle_sync.h"
+    },
     {
       "code_lines": 10,
       "path": "App/task/default_task.h"