sync: Shanghai-U9 2026-09-03 硬编码审计清掉 0819/0826 挂了两轮的文档类遗留

smod_atsc_dev（SKILL.md / references/imx6.md / references/fpga.md）、
fpga_update（SKILL.md / references/protocol.md）、fpga-imx6-flow（SKILL.md）
正文表格与 shell 示例里的 E:\Xilinx_design\smod\SMOD_ATSC\... 和 192.168.1.143
改成引用 skills_env.md 的 SMOD_REPO_ROOT / SMOD_BOARD_IP；shell 块统一用 $BOARD
并在块内注明取值出处。13 处锚点全部唯一命中，无行为改动。

刻意未改：各 skill 的 YAML description 里的同名字面量（那是触发关键词，不是
脚本取值，改了降低匹配率）；脚本里 _env_lookup(KEY, 字面量) 形式的回落默认值；
fpga_flash/SKILL.md 的 SMOD_DTMB_CG 命令示例（属另一个工程，无对应 env 键）。

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018FykpdV2Y4RUWXU5PtoLqh

fpga-imx6-flow/SKILL.md

@@ -192,7 +192,7 @@ Here is the working recipe for the `modify_imx6` interrupt (cross-compile HEAD's
 push it to the imx6). All of this is **network-based and fast** — no slow serial file push.
 
 **Hosts / creds**
-- **imx6 mgmt: `192.168.1.143`** (Windows host is on `192.168.1.125`, same subnet — `ping` works).
+- **imx6 mgmt: `SMOD_BOARD_IP` in `~\skills_env.md`** (the Windows host is on the same subnet — `ping` works).
   The old memory "imx6 not reachable over the network" is **outdated**; the mgmt port is reachable.
   Login: **`root`**, password = `SMOD_SSH_PASS` in `~\skills_env.md`. (The serial console still works too but its login auto-logs-out and
   is flaky; prefer network SSH for imx6 shell/log reads.)