Function apply_writeback_for_entry 

pub fn apply_writeback_for_entry(
    vault_root: &Path,
    entry: &LedgerEntry,
) -> Option<VaultWriteResult>

根据 LedgerEntry 的最新 state 做 vault 回写,错误降级为 stderr warn。

• Accepted / Canonical → 写/更新 note
• Archived → 打 archived 标记
• Draft / Candidate → 不回写 (schema: 审核后才 promote)