Renumber the pipeline substeps to match the paper (5-1 becomes 5a)

prompts/ and runs/ move by git mv; zero padding dropped; the
arbitration and LLM-merge rows in the cost ledger carry no new
name -- their step column reads 已廢棄 with the original name
kept in a new last column.  Archived meta.json files and past
decision-log entries keep the names they were written with.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/output-validation.md

@@ -1,11 +1,11 @@
 # LLM 輸出的契約查核
 
 （2026-08-06 量測。對象為步驟 3 的三份執行歸檔
-`runs/03-code/run1`–`run3`，共 883 首歌、44,149 筆標籤
+`runs/3a-code/run1`–`run3`，共 883 首歌、44,149 筆標籤
 指派、44,146 句引述。歌詞以模型實際看到的那一份為準，即
 `tools/instance/llm-input-code.jsonl`。）
 
-定義檔 `prompts/03-code.md` 對輸出下了四條明確要求：只用
+定義檔 `prompts/3a-code.md` 對輸出下了四條明確要求：只用
 給定的碼且拼寫照給、每個標出的碼恰引一行歌詞、引述逐字、
 輸出為合法 JSON 且無其他文字。本檔記錄這四條各自被遵守到
 什麼程度。