feat(屏板): 帧 B 组帧 + 中断起发 TX DMA + 按键队列 + 离线判定（批 2）

批 2 五项全部落地（docs/任务规划/屏板链路.md §3）：
- 2-1 sb_link_frame_update()：uiTask 渲染后按需组帧，不留 3200 B 影子
  副本，直接拿活显存与帧内点阵段 memcmp；组完自校验，过了才置 ready。
  静态 4208 B 帧缓冲实测落 RW_IRAM1（0x20006d98），不在 CCM。
- 2-2 空闲中断校完 6 B 召唤帧直接点 TX DMA（sb_tx_kick），不排队不攒批；
  busy 期间再来的召唤丢帧并计数，绝不叠发（屏板收帧一次 IDLE 一包）。
- 2-3 按键走环形队列（中断入、任务出），uiTask 按 §4.3 表映射 UI_KEY_*
  后调 ui_port_queue_key；9/10（RESET/FACTORY）按决策四先丢弃并留痕。
- 2-4 HAL_UART_TxCpltCallback 在 rs485.c 加第三行转发（三个全局回调
  落点收一处，防日后重复定义）；busy 冻结帧缓冲，错误中断按 gState
  收拾被打断的 TX，防残留 busy 把链路永久锁死。
- 2-5 连续 >=10 s 无有效召唤帧才判离线（不按 500 ms——屏板约 5000 s
  自复位有 1 s 空窗），恢复即清标志；CRC 错帧静默丢弃并计数。

实测：台架 40 s（PC 顶替屏板，--key-fixed 2 持续改画面）rx=143 ok=143
keys=143 crc=0 / tx=143 done=143 drop=0 abor=0 fb=144 bad=0；脚本一停
10 s 准点出 OFFLINE。组帧耗时 509 µs 典型 / 709 µs 峰值——原 0.3 ms
判据系估算，已按实测在规划文档改口为 1 ms 并给出压降路径（未做）。

附带：rs485_on_rx 补 CODE-RULE-09 文档块（本轮改 rs485.c 触发整文件
重扫被拦）；CRC 循环计数改 32 位（消掉 ARMCC 每轮 UXTH）；bench 脚本
加 --reply/--key-fixed/--dump，并写明 CH340 收不了 700 kbaud 连续流、
--reply 收不全 4208 B 不是固件问题。

主机单测 146/146 PASSED（+65）；Keil 0 错误 0 警告；ci_local 全绿
（SKIP=nested-comment，worktree 限制，主树脚本另查 0 新发）。
Code=238,936 B / RW_IRAM1 65.5 % / RW_CCM 87.9 %。

scripts/ram_baseline.tsv

@@ -11,4 +11,4 @@ date	code	ro	rw	zi	er_irom1	er_pct	iram1	iram1_pct	ccm	ccm_pct	top_rwzi
 2026-10-26	231712	25560	1520	136216	257272	24.5	80312	61.3	57376	87.9	heap_4.o=57376;lv_mem_core_builtin.o=16384;lftpd.o=7884;ui_net_sink.o=6770;ui_port.o=6420;nand_ftl.o=6216;ch395f.o=4162;console_log.o=4132;sys_log_mcu.o=4003;default_task.o=2736
 2026-10-27	235372	26392	1572	136924	261764	25.0	81072	61.9	57376	87.9	heap_4.o=57376;lv_mem_core_builtin.o=16384;lftpd.o=7884;ui_net_sink.o=6770;ui_port.o=6420;nand_ftl.o=6216;ch395f.o=4162;console_log.o=4132;sys_log_mcu.o=4055;default_task.o=2736
 2026-10-28	236456	28124	1876	137084	264580	25.2	81536	62.2	57376	87.9	heap_4.o=57376;lv_mem_core_builtin.o=16384;lftpd.o=7884;ui_net_sink.o=6770;ui_port.o=6420;nand_ftl.o=6216;ch395f.o=4162;console_log.o=4132;sys_log_mcu.o=4055;default_task.o=2736
-2026-10-29	237464	28896	1900	137140	266360	25.4	81616	62.3	57376	87.9	heap_4.o=57376;lv_mem_core_builtin.o=16384;lftpd.o=7884;ui_net_sink.o=6770;ui_port.o=6420;nand_ftl.o=6216;ch395f.o=4162;console_log.o=4132;sys_log_mcu.o=4055;default_task.o=2736
+2026-10-29	238936	29140	1932	141396	268076	25.6	85904	65.5	57376	87.9	heap_4.o=57376;lv_mem_core_builtin.o=16384;lftpd.o=7884;ui_net_sink.o=6770;ui_port.o=6420;nand_ftl.o=6216;sb_link.o=4364;ch395f.o=4162;console_log.o=4132;sys_log_mcu.o=4055

scripts/size_attestation.json

@@ -1,25 +1,25 @@
 {
-  "built_at": "2026-10-29T20:05:10+08:00",
-  "fingerprint": "aff51072f981be06701568ea469dd4baa0278299ac530446feb299ac0cba8abd",
+  "built_at": "2026-10-29T20:54:02+08:00",
+  "fingerprint": "1297b04cfaed4c9b8c30a1fcc64608932d3d047a32ad687274a6eac40bc4ca45",
   "fingerprint_files": 1456,
   "fingerprint_source": "git-index",
   "gated_regions": [
     "RW_IRAM1",
     "RW_CCM"
   ],
-  "git_head": "2c69a6ca076d201a2f412318bdfaa91f20632c48",
+  "git_head": "e5b4182a9f02dfe9f1f06dd58d086f64a157cc5c",
   "map": "MDK-ARM/STM32F407-Demo/STM32F407-Demo.map",
-  "map_mtime": 1793275502,
+  "map_mtime": 1793278440,
   "pct": {
-    "ER_IROM1": 25.4,
+    "ER_IROM1": 25.57,
     "RW_CCM": 87.89,
-    "RW_IRAM1": 62.27,
+    "RW_IRAM1": 65.54,
     "UNINIT_CCM": 18.75
   },
   "regions": {
     "ER_IROM1": {
       "max": 1048576,
-      "size": 266360
+      "size": 268076
     },
     "RW_CCM": {
       "max": 65280,
@@ -27,7 +27,7 @@
     },
     "RW_IRAM1": {
       "max": 131072,
-      "size": 81616
+      "size": 85904
     },
     "UNINIT_CCM": {
       "max": 256,
@@ -37,10 +37,10 @@
   "schema": 2,
   "scope_note": "\u540c\u7801\u51ed\u8bc1\uff1a\u6307\u7eb9\u8986\u76d6\u56fa\u4ef6\u4f53\u79ef\u76f8\u5173\u6e90\u7801\uff0c\u53e3\u5f84\u89c1\u672c\u811a\u672c docstring",
   "sizes": {
-    "code": 237464,
-    "ro_data": 28896,
-    "rw_data": 1900,
-    "zi_data": 137140
+    "code": 238936,
+    "ro_data": 29140,
+    "rw_data": 1932,
+    "zi_data": 141396
   },
   "threshold_pct": 92.0,
   "worktree_dirt_at_stamp": 0,

scripts/test_coverage_baseline.json

@@ -346,19 +346,19 @@
     },
     "Drivers/BSP/ScreenLink/sb_link.c": {
       "func_rate": 1.0,
-      "funcs_covered": 7,
-      "funcs_valid": 7,
-      "line_rate": 0.9896,
-      "lines_covered": 95,
-      "lines_valid": 96
+      "funcs_covered": 13,
+      "funcs_valid": 13,
+      "line_rate": 0.971,
+      "lines_covered": 201,
+      "lines_valid": 207
     },
     "Drivers/BSP/ScreenLink/sb_proto.c": {
       "func_rate": 1.0,
       "funcs_covered": 6,
       "funcs_valid": 6,
       "line_rate": 1.0,
-      "lines_covered": 74,
-      "lines_valid": 74
+      "lines_covered": 75,
+      "lines_valid": 75
     },
     "Drivers/BSP/UI/ui_data.c": {
       "func_rate": 0.9767,
@@ -625,17 +625,17 @@
     },
     "sb_link": {
       "files": {
-        "Drivers/BSP/ScreenLink/sb_link.c": 96,
-        "Drivers/BSP/ScreenLink/sb_proto.c": 74
+        "Drivers/BSP/ScreenLink/sb_link.c": 207,
+        "Drivers/BSP/ScreenLink/sb_proto.c": 75
       },
-      "lines_total": 170,
+      "lines_total": 282,
       "ok": true
     },
     "sb_proto": {
       "files": {
-        "Drivers/BSP/ScreenLink/sb_proto.c": 74
+        "Drivers/BSP/ScreenLink/sb_proto.c": 75
       },
-      "lines_total": 74,
+      "lines_total": 75,
       "ok": true
     },
     "sha256": {
@@ -782,12 +782,12 @@
     "files_generated_excluded": 5,
     "files_tested": 48,
     "files_untested": 165,
-    "func_rate": 0.9332,
-    "funcs_covered": 545,
-    "funcs_valid": 584,
-    "line_rate": 0.9003,
-    "lines_covered": 7227,
-    "lines_valid": 8027,
+    "func_rate": 0.9339,
+    "funcs_covered": 551,
+    "funcs_valid": 590,
+    "line_rate": 0.9011,
+    "lines_covered": 7334,
+    "lines_valid": 8139,
     "modules_ok": 43,
     "modules_total": 43
   },
@@ -833,12 +833,12 @@
       "path": "App/task/adc_task.c"
     },
     {
-      "code_lines": 218,
-      "path": "Drivers/BSP/UI/ui_page_clock.c"
+      "code_lines": 245,
+      "path": "App/task/ui_task.c"
     },
     {
-      "code_lines": 215,
-      "path": "App/task/ui_task.c"
+      "code_lines": 218,
+      "path": "Drivers/BSP/UI/ui_page_clock.c"
     },
     {
       "code_lines": 215,
@@ -929,12 +929,12 @@
       "path": "Drivers/BSP/UI/ui_page_yx.c"
     },
     {
-      "code_lines": 83,
-      "path": "Drivers/BSP/NET/net_socket.h"
+      "code_lines": 84,
+      "path": "Drivers/BSP/RS485/rs485.c"
     },
     {
-      "code_lines": 81,
-      "path": "Drivers/BSP/RS485/rs485.c"
+      "code_lines": 83,
+      "path": "Drivers/BSP/NET/net_socket.h"
     },
     {
       "code_lines": 79,
@@ -980,6 +980,10 @@
       "code_lines": 50,
       "path": "App/log/sys_log.h"
     },
+    {
+      "code_lines": 50,
+      "path": "Drivers/BSP/ScreenLink/sb_link.h"
+    },
     {
       "code_lines": 47,
       "path": "Drivers/BSP/UI/ui_w_soe.h"
@@ -1060,10 +1064,6 @@
       "code_lines": 33,
       "path": "Drivers/BSP/NET/net_select.h"
     },
-    {
-      "code_lines": 33,
-      "path": "Drivers/BSP/ScreenLink/sb_link.h"
-    },
     {
       "code_lines": 33,
       "path": "Drivers/BSP/UI/ui_page_action.h"