fix(agentmain): make /resume fall back to L4 archives (v2, re-roll onto current main)

[Kailigithub]

Summary

Extend the /resume slash command prompt so the agent falls back to L4 archive artifacts (all_histories.txt, {YYYY-MM}.zip in memory/L4_raw_sessions/) when fewer than 5 raw .txt files remain in temp/model_responses/.

Problem

memory/L4_raw_sessions/compress_session.py archives raw session .txt files once it merges them into all_histories.txt and the monthly {YYYY-MM}.zip archives. The /resume handler in agentmain.py hardcoded the prompt to read temp/model_responses/ only — so users who ran /resume after L4 archival completed saw an empty session list, even though their history was recoverable from the archives.

Fix

Single-source change in agentmain.py: extend the /resume prompt so the agent first tries temp/model_responses/ (live), and on <5 files remaining falls back to memory/L4_raw_sessions/all_histories.txt (consolidated history) or memory/L4_raw_sessions/{YYYY-MM}.zip (monthly archive).

if raw_query.strip() == '/resume':
    return (r'帮我看看最近有哪些会话可以恢复。'
            r'先列 temp/model_responses/ 目录（按修改时间取最近10个文件）。'
            r'如果该目录里的 .txt 少于 5 个（L4 归档已清理原始文件），'
            r'回退读 memory/L4_raw_sessions/all_histories.txt（汇总的会话历史），'
            r'或解压 memory/L4_raw_sessions/{YYYY-MM}.zip 取最近的月度归档。'
            r'从每个文件里找最后一个<history>...</history>块，'
            r'用一句话总结每个会话在聊什么，列表给我选。'
            r'注意读文件后要把字面的\n替换成真换行才能正确匹配。')

Verification

• python3 -m py_compile agentmain.py — syntax OK
• Regression harness at /tmp/test_issue_630.py — 4 checks:
  • test_old_prompt_gone: confirms the original /resume prompt string was removed.
  • test_new_prompt_present: confirms all_histories.txt, memory/L4_raw_sessions, {YYYY-MM}.zip, and 少于 5 个 (fallback threshold) are all present.
  • test_resume_branch_still_wired: confirms if raw_query.strip() == '/resume': is still in the file.
  • test_resume_returns_nonempty_string: confirms the return statement still starts with the resume directive.
• Three-step dance (stash → test fails on main → pop → test passes with fix) confirms the test catches the regression.

Scope

• 1 file, +8/-1 lines
• Pure prompt string change — no runtime logic, no schema impact, no migration
• Closes /resume 在 L4 会话归档后失效，无法感知已归档的历史会话 #630