docs(arch): Add ARCHITECTURE and CLAUDE, init repo

Bring the Diag-OS variant of the Blanton A/B/C Tera Term scripts under
version control, alongside the SONiC-based Blanton_TTL_Script.

- ARCHITECTURE.md: Diag OS flow, acc_* command taxonomy, swutil addressing,
  TH6 test sequence side effects, and a 6-phase roadmap
- CLAUDE.md: stack, per-script command inventory, conventions, footguns
- .gitattributes: keep .ttl as CRLF (Windows-only), LF for everything else
- .gitignore: secret/, For_AI/, *.log, publish/ output
- secret/: README + config_secret.ttl.example for per-unit overrides
- Logs/ and utils/ placeholders (logopen needs Logs/ to pre-exist)

Known gaps documented, not fixed here: 2_Blanton_Script_B.ttl includes
utils/show_margin_status.ttl which does not exist yet, and its while loop
has no pause despite the "every 10mins" comment.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SoEiorvuhmdTkpZWtEhJwq

.gitattributes

@@ -0,0 +1,28 @@
+# =============================================================================
+# 換行符政策
+# -----------------------------------------------------------------------------
+# 這個 repo 的 .ttl 只在 Windows（Tera Term）上跑，其餘文字檔可能在 Linux 上處理，
+# 所以必須明確指定，不能靠各機器的 core.autocrlf。
+#
+# 姊妹專案 Blanton_TTL_Script 踩過的坑：bash 腳本帶著 CRLF 進 repo，
+# scp 到 DUT 後直接掛（-bash: $'\r': command not found）。
+# 本專案目前沒有 .sh，但規則先立好，之後加工具腳本就不會再踩。
+# =============================================================================
+
+# Tera Term macro 只在 Windows 上跑，維持 CRLF；標成 -text 讓 git 原樣保存，
+# 避免對既有檔案產生大量純換行符的假 diff
+*.ttl   -text
+
+# 在 Linux 上執行或被 source 的，一律 LF
+*.sh    text eol=lf
+*.conf  text eol=lf
+*.py    text eol=lf
+*.yml   text eol=lf
+*.txt   text eol=lf
+*.md    text eol=lf
+
+# 二進位，不要做任何轉換
+*.xlsx  binary
+*.docx  binary
+*.pdf   binary
+*.h5    binary